<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2025 Workiva-->
<!--r:37750184-17ad-43a4-8e81-df8a32152432,g:27524611-a6cf-4fd1-8ddd-550fe4e71a44-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.westlake.com/role/CoverPage" xlink:type="simple" xlink:href="wlk-20250331.xsd#CoverPage"/>
  <link:definitionLink xlink:role="http://www.westlake.com/role/CoverPage" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_184970bc-7506-4f81-82f5-788bc8ae4e4a" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_DocumentInformationTable_184970bc-7506-4f81-82f5-788bc8ae4e4a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_e0647754-2671-4684-8461-d623d6f291e1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_184970bc-7506-4f81-82f5-788bc8ae4e4a" xlink:to="loc_us-gaap_StatementClassOfStockAxis_e0647754-2671-4684-8461-d623d6f291e1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_e0647754-2671-4684-8461-d623d6f291e1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_e0647754-2671-4684-8461-d623d6f291e1" xlink:to="loc_us-gaap_ClassOfStockDomain_e0647754-2671-4684-8461-d623d6f291e1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_757fa522-3629-4ff4-a7f9-f635e65696e5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_e0647754-2671-4684-8461-d623d6f291e1" xlink:to="loc_us-gaap_ClassOfStockDomain_757fa522-3629-4ff4-a7f9-f635e65696e5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_80559194-fe60-4868-b6d9-d59c690ad626" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_757fa522-3629-4ff4-a7f9-f635e65696e5" xlink:to="loc_us-gaap_CommonStockMember_80559194-fe60-4868-b6d9-d59c690ad626" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_OnePointSixTwoFivePercentageSeniorNotesDueTwentyTwentyNineMember_a2a7703a-6075-4121-bf6c-c4901122b26d" xlink:href="wlk-20250331.xsd#wlk_OnePointSixTwoFivePercentageSeniorNotesDueTwentyTwentyNineMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_757fa522-3629-4ff4-a7f9-f635e65696e5" xlink:to="loc_wlk_OnePointSixTwoFivePercentageSeniorNotesDueTwentyTwentyNineMember_a2a7703a-6075-4121-bf6c-c4901122b26d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_6cac7749-ee59-40e7-9134-79fcb7eee587" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_DocumentType_6cac7749-ee59-40e7-9134-79fcb7eee587" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_cccd5bfd-0d6d-4fb0-b75a-9e5391bd5d51" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_DocumentQuarterlyReport_cccd5bfd-0d6d-4fb0-b75a-9e5391bd5d51" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_1007fa6f-9e65-477a-9477-c39e5357bf25" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_DocumentPeriodEndDate_1007fa6f-9e65-477a-9477-c39e5357bf25" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_ff5f7ba9-5508-4ed9-84d9-212f7dac1e72" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_DocumentTransitionReport_ff5f7ba9-5508-4ed9-84d9-212f7dac1e72" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_1ef8a2f2-55d3-4ad1-a9fb-b7da7c2a4d3a" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_EntityFileNumber_1ef8a2f2-55d3-4ad1-a9fb-b7da7c2a4d3a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_c5af0d60-5e81-49ea-9b54-74cc448ef0e1" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_EntityRegistrantName_c5af0d60-5e81-49ea-9b54-74cc448ef0e1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_3563e02b-0967-4c7a-8955-4b91d931cc44" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_EntityIncorporationStateCountryCode_3563e02b-0967-4c7a-8955-4b91d931cc44" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_59c0c49b-1330-492f-b9b0-4d684d92b16f" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_EntityTaxIdentificationNumber_59c0c49b-1330-492f-b9b0-4d684d92b16f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_b0a62478-8023-4d00-8ec8-6dd6bdba4999" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_EntityAddressAddressLine1_b0a62478-8023-4d00-8ec8-6dd6bdba4999" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine2_181666de-07c7-4e03-9fa3-8c903bf4c708" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressAddressLine2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_EntityAddressAddressLine2_181666de-07c7-4e03-9fa3-8c903bf4c708" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_e6c52874-3f2d-4a71-93b8-5e41b79c7dc4" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_EntityAddressCityOrTown_e6c52874-3f2d-4a71-93b8-5e41b79c7dc4" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_27a84b8b-745e-46b7-8261-5781e3283387" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_EntityAddressStateOrProvince_27a84b8b-745e-46b7-8261-5781e3283387" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_c3cb7ec5-c777-475a-b94f-610a38303c71" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_EntityAddressPostalZipCode_c3cb7ec5-c777-475a-b94f-610a38303c71" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_2c0c4ffa-ed63-4c01-8227-6a3f3a504b3e" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_CityAreaCode_2c0c4ffa-ed63-4c01-8227-6a3f3a504b3e" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_bded81bf-f789-4870-843e-7fd92aee9fdf" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_LocalPhoneNumber_bded81bf-f789-4870-843e-7fd92aee9fdf" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_42626d75-441a-44b6-964c-6a9e0ee86726" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_Security12bTitle_42626d75-441a-44b6-964c-6a9e0ee86726" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_42d51471-db5f-48e6-aacb-ff6346864dc5" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_TradingSymbol_42d51471-db5f-48e6-aacb-ff6346864dc5" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_9c8fd41f-d356-4834-914c-a2144619b565" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_SecurityExchangeName_9c8fd41f-d356-4834-914c-a2144619b565" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_dee438d2-5e20-4a25-9427-1743af233a2c" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_EntityCurrentReportingStatus_dee438d2-5e20-4a25-9427-1743af233a2c" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_8856a943-a5d6-4477-8827-ea807031754d" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_EntityInteractiveDataCurrent_8856a943-a5d6-4477-8827-ea807031754d" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_08a983b4-f70f-42d9-b5fc-53d5ad3b3f30" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_EntityFilerCategory_08a983b4-f70f-42d9-b5fc-53d5ad3b3f30" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_65b1ae05-1146-40a3-88a4-691a3c4c290f" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_EntitySmallBusiness_65b1ae05-1146-40a3-88a4-691a3c4c290f" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_3c5687c8-3ee7-4d36-9925-f60aecce8bb1" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_EntityEmergingGrowthCompany_3c5687c8-3ee7-4d36-9925-f60aecce8bb1" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_9c025b09-ebfb-407e-908f-653821aafe1f" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_EntityShellCompany_9c025b09-ebfb-407e-908f-653821aafe1f" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_ee761c92-9532-4c9a-8634-8325520b918b" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_ee761c92-9532-4c9a-8634-8325520b918b" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_8183c7d0-b5de-4d86-9833-5c687d2eca09" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_AmendmentFlag_8183c7d0-b5de-4d86-9833-5c687d2eca09" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_74b59e11-8b33-403e-9ab9-30c2cda7eb88" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_DocumentFiscalYearFocus_74b59e11-8b33-403e-9ab9-30c2cda7eb88" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_91eb0218-3be6-4bfa-a35d-292fb7e853f4" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_DocumentFiscalPeriodFocus_91eb0218-3be6-4bfa-a35d-292fb7e853f4" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_c89d7567-d86e-455d-9e9a-01330c0cfe8c" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_EntityCentralIndexKey_c89d7567-d86e-455d-9e9a-01330c0cfe8c" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_b7100ac2-74e6-4a75-8ec2-da96741b8042" xlink:href="https://xbrl.sec.gov/dei/2024/dei-2024.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_aac47266-1d6a-4668-a8b4-996df8323c26" xlink:to="loc_dei_CurrentFiscalYearEndDate_b7100ac2-74e6-4a75-8ec2-da96741b8042" xlink:type="arc" order="29"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.westlake.com/role/ConsolidatedBalanceSheetsUnauditedParenthetical" xlink:type="simple" xlink:href="wlk-20250331.xsd#ConsolidatedBalanceSheetsUnauditedParenthetical"/>
  <link:definitionLink xlink:role="http://www.westlake.com/role/ConsolidatedBalanceSheetsUnauditedParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_56367572-cd01-4c60-9c24-24c4feac3d09" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_e9984093-df81-40bb-89d4-39c837475aa8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_56367572-cd01-4c60-9c24-24c4feac3d09" xlink:to="loc_us-gaap_StatementTable_e9984093-df81-40bb-89d4-39c837475aa8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_2ab882e6-1b25-4fbc-ba38-daeee5ec2c0d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_e9984093-df81-40bb-89d4-39c837475aa8" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_2ab882e6-1b25-4fbc-ba38-daeee5ec2c0d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_2ab882e6-1b25-4fbc-ba38-daeee5ec2c0d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_2ab882e6-1b25-4fbc-ba38-daeee5ec2c0d" xlink:to="loc_us-gaap_EquityComponentDomain_2ab882e6-1b25-4fbc-ba38-daeee5ec2c0d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_056ffd4a-1f61-46ba-8564-239233a44c42" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_2ab882e6-1b25-4fbc-ba38-daeee5ec2c0d" xlink:to="loc_us-gaap_EquityComponentDomain_056ffd4a-1f61-46ba-8564-239233a44c42" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_1fc69f8f-f598-48dd-84ec-9ad1407af58b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_056ffd4a-1f61-46ba-8564-239233a44c42" xlink:to="loc_us-gaap_CommonStockMember_1fc69f8f-f598-48dd-84ec-9ad1407af58b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_7c6f0786-bf19-4580-a395-f064be767ce9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_056ffd4a-1f61-46ba-8564-239233a44c42" xlink:to="loc_us-gaap_TreasuryStockCommonMember_7c6f0786-bf19-4580-a395-f064be767ce9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockParOrStatedValuePerShare_92c4b030-a58a-4302-b1b5-74bf159624dd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_56367572-cd01-4c60-9c24-24c4feac3d09" xlink:to="loc_us-gaap_PreferredStockParOrStatedValuePerShare_92c4b030-a58a-4302-b1b5-74bf159624dd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesAuthorized_cdad68c5-eab0-4e2e-8a81-3d0c0d2959c6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_56367572-cd01-4c60-9c24-24c4feac3d09" xlink:to="loc_us-gaap_PreferredStockSharesAuthorized_cdad68c5-eab0-4e2e-8a81-3d0c0d2959c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_9deb5a95-90ce-467b-ae01-b3399373c0ad" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PreferredStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_56367572-cd01-4c60-9c24-24c4feac3d09" xlink:to="loc_us-gaap_PreferredStockSharesOutstanding_9deb5a95-90ce-467b-ae01-b3399373c0ad" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_9b1a5c0b-92b3-44cd-8a85-86d3d0f9542a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_56367572-cd01-4c60-9c24-24c4feac3d09" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_9b1a5c0b-92b3-44cd-8a85-86d3d0f9542a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_2a164ab8-c2c9-4a3e-9639-e35f38ec1c80" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_56367572-cd01-4c60-9c24-24c4feac3d09" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_2a164ab8-c2c9-4a3e-9639-e35f38ec1c80" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_6f6ffd29-75a5-4229-9c46-76b19d7185b5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_56367572-cd01-4c60-9c24-24c4feac3d09" xlink:to="loc_us-gaap_CommonStockSharesIssued_6f6ffd29-75a5-4229-9c46-76b19d7185b5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonShares_2c2c2770-748f-471c-af3a-cf79ee3ebcc7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockCommonShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_56367572-cd01-4c60-9c24-24c4feac3d09" xlink:to="loc_us-gaap_TreasuryStockCommonShares_2c2c2770-748f-471c-af3a-cf79ee3ebcc7" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.westlake.com/role/ConsolidatedStatementsOfChangesInStockholdersEquity" xlink:type="simple" xlink:href="wlk-20250331.xsd#ConsolidatedStatementsOfChangesInStockholdersEquity"/>
  <link:definitionLink xlink:role="http://www.westlake.com/role/ConsolidatedStatementsOfChangesInStockholdersEquity" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_60018ebd-e977-497a-b8bd-46b7311d813c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_77394703-cf20-4b94-8b3a-e468730bd03c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_60018ebd-e977-497a-b8bd-46b7311d813c" xlink:to="loc_us-gaap_StatementTable_77394703-cf20-4b94-8b3a-e468730bd03c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_a0fc3425-9ac2-45f6-a463-d63a2666e828" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_77394703-cf20-4b94-8b3a-e468730bd03c" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_a0fc3425-9ac2-45f6-a463-d63a2666e828" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_a0fc3425-9ac2-45f6-a463-d63a2666e828_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_a0fc3425-9ac2-45f6-a463-d63a2666e828" xlink:to="loc_us-gaap_EquityComponentDomain_a0fc3425-9ac2-45f6-a463-d63a2666e828_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_11bf82f8-4b14-48f4-986c-0334d48ea554" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_a0fc3425-9ac2-45f6-a463-d63a2666e828" xlink:to="loc_us-gaap_EquityComponentDomain_11bf82f8-4b14-48f4-986c-0334d48ea554" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_b475f096-3b01-4783-bec8-172cba21a798" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_11bf82f8-4b14-48f4-986c-0334d48ea554" xlink:to="loc_us-gaap_CommonStockMember_b475f096-3b01-4783-bec8-172cba21a798" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_340700b4-06f5-4bab-b750-c326fe6bd65c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_11bf82f8-4b14-48f4-986c-0334d48ea554" xlink:to="loc_us-gaap_TreasuryStockCommonMember_340700b4-06f5-4bab-b750-c326fe6bd65c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_cc0c0661-44b2-4e96-aa95-0deb893f957c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_11bf82f8-4b14-48f4-986c-0334d48ea554" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_cc0c0661-44b2-4e96-aa95-0deb893f957c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_733def7b-3395-4876-a0b8-9a85a7ea294e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_11bf82f8-4b14-48f4-986c-0334d48ea554" xlink:to="loc_us-gaap_RetainedEarningsMember_733def7b-3395-4876-a0b8-9a85a7ea294e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_98b41846-703c-4ba6-bacc-1cae33f862b1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_11bf82f8-4b14-48f4-986c-0334d48ea554" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_98b41846-703c-4ba6-bacc-1cae33f862b1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_d240e8a1-b3a7-4716-8b56-c1dd9e6dbf04" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_11bf82f8-4b14-48f4-986c-0334d48ea554" xlink:to="loc_us-gaap_NoncontrollingInterestMember_d240e8a1-b3a7-4716-8b56-c1dd9e6dbf04" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d6ae0542-2e2b-41d0-a2c1-8ff9cc835a03" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_60018ebd-e977-497a-b8bd-46b7311d813c" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d6ae0542-2e2b-41d0-a2c1-8ff9cc835a03" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_7739565e-5d7f-4b54-83cb-c6caacd86cfd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d6ae0542-2e2b-41d0-a2c1-8ff9cc835a03" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_7739565e-5d7f-4b54-83cb-c6caacd86cfd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_892cb6fa-2dd3-4510-a3ce-a5fb1d3b4344" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d6ae0542-2e2b-41d0-a2c1-8ff9cc835a03" xlink:to="loc_us-gaap_CommonStockSharesIssued_892cb6fa-2dd3-4510-a3ce-a5fb1d3b4344" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonShares_8f18e11e-f53f-49a1-8040-dc7a90d3b176" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockCommonShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d6ae0542-2e2b-41d0-a2c1-8ff9cc835a03" xlink:to="loc_us-gaap_TreasuryStockCommonShares_8f18e11e-f53f-49a1-8040-dc7a90d3b176" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_2300bcd3-50e6-4861-837f-33ebad7bf9fc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d6ae0542-2e2b-41d0-a2c1-8ff9cc835a03" xlink:to="loc_us-gaap_ProfitLoss_2300bcd3-50e6-4861-837f-33ebad7bf9fc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_93d1000d-b1d9-4937-a35e-9105c4ab42db" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d6ae0542-2e2b-41d0-a2c1-8ff9cc835a03" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_93d1000d-b1d9-4937-a35e-9105c4ab42db" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_ba7358a4-cb1f-4972-b3c3-0cb27c73203a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d6ae0542-2e2b-41d0-a2c1-8ff9cc835a03" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_ba7358a4-cb1f-4972-b3c3-0cb27c73203a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_fad6d5f6-5bdd-46f2-9b99-a5e9a6cd3f97" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d6ae0542-2e2b-41d0-a2c1-8ff9cc835a03" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_fad6d5f6-5bdd-46f2-9b99-a5e9a6cd3f97" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_4bb4002b-4e9f-4797-84ed-e5c355fe8b53" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d6ae0542-2e2b-41d0-a2c1-8ff9cc835a03" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_4bb4002b-4e9f-4797-84ed-e5c355fe8b53" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_2c58d108-8057-4b7d-9813-7f4a7bfd0883" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d6ae0542-2e2b-41d0-a2c1-8ff9cc835a03" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_2c58d108-8057-4b7d-9813-7f4a7bfd0883" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_714e7442-bce6-4753-828a-05abdb53ff42" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d6ae0542-2e2b-41d0-a2c1-8ff9cc835a03" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_714e7442-bce6-4753-828a-05abdb53ff42" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStockCash_3be82a56-687e-4392-be9b-1884c2d9c573" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DividendsCommonStockCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d6ae0542-2e2b-41d0-a2c1-8ff9cc835a03" xlink:to="loc_us-gaap_DividendsCommonStockCash_3be82a56-687e-4392-be9b-1884c2d9c573" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_a9bb23e3-2634-4a93-a4cd-23f0f3b40b5c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_d6ae0542-2e2b-41d0-a2c1-8ff9cc835a03" xlink:to="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_a9bb23e3-2634-4a93-a4cd-23f0f3b40b5c" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_0c2f2df8-e29e-434e-b742-2c35e16d00c0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_1bfa923b-f5d9-45ce-83d7-0a6d969165e3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonShares_68b5d817-6ec6-4420-abbe-4edcf16e6e44" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockCommonShares"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.westlake.com/role/FinancialInstrumentsCostandFairValueofAvailableForSaleDebtSecuritiesDetails" xlink:type="simple" xlink:href="wlk-20250331.xsd#FinancialInstrumentsCostandFairValueofAvailableForSaleDebtSecuritiesDetails"/>
  <link:definitionLink xlink:role="http://www.westlake.com/role/FinancialInstrumentsCostandFairValueofAvailableForSaleDebtSecuritiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_a37d86cb-8474-4976-9db5-e74cee21195c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_1ba47b8b-6129-4fce-aa0e-c050c6fa23a6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_a37d86cb-8474-4976-9db5-e74cee21195c" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_1ba47b8b-6129-4fce-aa0e-c050c6fa23a6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_705aba9d-cc0c-4f1c-80e3-c676180f0e72" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_1ba47b8b-6129-4fce-aa0e-c050c6fa23a6" xlink:to="loc_us-gaap_FinancialInstrumentAxis_705aba9d-cc0c-4f1c-80e3-c676180f0e72" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_705aba9d-cc0c-4f1c-80e3-c676180f0e72_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_705aba9d-cc0c-4f1c-80e3-c676180f0e72" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_705aba9d-cc0c-4f1c-80e3-c676180f0e72_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_36630dbc-0a20-4ffd-9892-d682a11cb605" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_705aba9d-cc0c-4f1c-80e3-c676180f0e72" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_36630dbc-0a20-4ffd-9892-d682a11cb605" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateDebtSecuritiesMember_2b9cc638-457d-46bb-9fa3-20154b8517c4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CorporateDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_36630dbc-0a20-4ffd-9892-d682a11cb605" xlink:to="loc_us-gaap_CorporateDebtSecuritiesMember_2b9cc638-457d-46bb-9fa3-20154b8517c4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_1bcc9d8f-fc91-4429-86ed-0e22be0cf006" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_36630dbc-0a20-4ffd-9892-d682a11cb605" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_1bcc9d8f-fc91-4429-86ed-0e22be0cf006" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_690faf6e-6af1-48b7-a47c-5dda672b81fe" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_36630dbc-0a20-4ffd-9892-d682a11cb605" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_690faf6e-6af1-48b7-a47c-5dda672b81fe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_daa95a6b-1417-4363-bb21-c7c7a2d6dd4c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_36630dbc-0a20-4ffd-9892-d682a11cb605" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_daa95a6b-1417-4363-bb21-c7c7a2d6dd4c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_SupranationalSecuritiesMember_12672f6c-8e51-4d9c-b37b-7335f2708823" xlink:href="wlk-20250331.xsd#wlk_SupranationalSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_36630dbc-0a20-4ffd-9892-d682a11cb605" xlink:to="loc_wlk_SupranationalSecuritiesMember_12672f6c-8e51-4d9c-b37b-7335f2708823" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAbstract_379b31bb-5b2d-42e7-8459-2d9672eca5c6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleSecuritiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_a37d86cb-8474-4976-9db5-e74cee21195c" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAbstract_379b31bb-5b2d-42e7-8459-2d9672eca5c6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_44072e90-cf15-4e1e-8401-dd1a52f4f4e5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_379b31bb-5b2d-42e7-8459-2d9672eca5c6" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_44072e90-cf15-4e1e-8401-dd1a52f4f4e5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_1001c40a-3145-4233-90ed-f6dbbb3d11c6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_379b31bb-5b2d-42e7-8459-2d9672eca5c6" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_1001c40a-3145-4233-90ed-f6dbbb3d11c6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAbstract_3db1220b-a71e-4912-b543-cbaf1aae4b08" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_a37d86cb-8474-4976-9db5-e74cee21195c" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAbstract_3db1220b-a71e-4912-b543-cbaf1aae4b08" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_6a498e58-3c3e-4ad2-b25b-ee4552ade8b9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAbstract_3db1220b-a71e-4912-b543-cbaf1aae4b08" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_6a498e58-3c3e-4ad2-b25b-ee4552ade8b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost_7e0a4214-6968-4f42-a521-96f8010c2e56" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_6a498e58-3c3e-4ad2-b25b-ee4552ade8b9" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost_7e0a4214-6968-4f42-a521-96f8010c2e56" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost_e8141e99-34c3-4ce5-87ca-b18a906e0c0e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_6a498e58-3c3e-4ad2-b25b-ee4552ade8b9" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost_e8141e99-34c3-4ce5-87ca-b18a906e0c0e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost_c671b79d-44b9-4aef-bc06-47494e398590" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCostAbstract_6a498e58-3c3e-4ad2-b25b-ee4552ade8b9" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost_c671b79d-44b9-4aef-bc06-47494e398590" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_796ed024-c1ce-499c-b818-6771f72cd46d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_41a92127-ece2-4241-b32a-4fea848e1811" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAbstract_3db1220b-a71e-4912-b543-cbaf1aae4b08" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_41a92127-ece2-4241-b32a-4fea848e1811" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_bdfeff88-ec01-4d74-a81f-087210eb6848" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_41a92127-ece2-4241-b32a-4fea848e1811" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_bdfeff88-ec01-4d74-a81f-087210eb6848" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_c3516629-f35e-444e-b0e6-9e221dc45506" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_41a92127-ece2-4241-b32a-4fea848e1811" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_c3516629-f35e-444e-b0e6-9e221dc45506" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue_e4277d52-b688-4318-a6a4-5c60ed5602c1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_41a92127-ece2-4241-b32a-4fea848e1811" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue_e4277d52-b688-4318-a6a4-5c60ed5602c1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_ad546b9b-93a6-4e25-b929-f73cba947270" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.westlake.com/role/AccountsReceivableDetails" xlink:type="simple" xlink:href="wlk-20250331.xsd#AccountsReceivableDetails"/>
  <link:definitionLink xlink:role="http://www.westlake.com/role/AccountsReceivableDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_e4e16bae-a6be-4103-8b5e-7bc03b0ffa02" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccountsNotesAndLoansReceivableLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_ff4b059f-efc2-40ab-afa5-042566410efb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_e4e16bae-a6be-4103-8b5e-7bc03b0ffa02" xlink:to="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_ff4b059f-efc2-40ab-afa5-042566410efb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_f42d0b4a-3691-40dc-b49d-0d3ed5ba2f7a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_ff4b059f-efc2-40ab-afa5-042566410efb" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_f42d0b4a-3691-40dc-b49d-0d3ed5ba2f7a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_f42d0b4a-3691-40dc-b49d-0d3ed5ba2f7a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_f42d0b4a-3691-40dc-b49d-0d3ed5ba2f7a" xlink:to="loc_us-gaap_RelatedPartyDomain_f42d0b4a-3691-40dc-b49d-0d3ed5ba2f7a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_09219900-1ec3-44d1-88af-dd74e452a4b3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_f42d0b4a-3691-40dc-b49d-0d3ed5ba2f7a" xlink:to="loc_us-gaap_RelatedPartyDomain_09219900-1ec3-44d1-88af-dd74e452a4b3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrelatedPartyMember_752f11b5-7b8a-4044-9fa2-a220bb6f5ecd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NonrelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_09219900-1ec3-44d1-88af-dd74e452a4b3" xlink:to="loc_us-gaap_NonrelatedPartyMember_752f11b5-7b8a-4044-9fa2-a220bb6f5ecd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_63b8ff14-d576-4390-b461-d691ceaab25b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_09219900-1ec3-44d1-88af-dd74e452a4b3" xlink:to="loc_us-gaap_RelatedPartyMember_63b8ff14-d576-4390-b461-d691ceaab25b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableGrossCurrent_55c7f4fa-1850-4aed-b68a-2668dbfc67c7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccountsReceivableGrossCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_e4e16bae-a6be-4103-8b5e-7bc03b0ffa02" xlink:to="loc_us-gaap_AccountsReceivableGrossCurrent_55c7f4fa-1850-4aed-b68a-2668dbfc67c7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_ee0bf939-066e-47de-af38-b328ce436d9d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_e4e16bae-a6be-4103-8b5e-7bc03b0ffa02" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_ee0bf939-066e-47de-af38-b328ce436d9d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_5cb3878c-73d7-499c-ae31-bc0d17865c0d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_e4e16bae-a6be-4103-8b5e-7bc03b0ffa02" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_5cb3878c-73d7-499c-ae31-bc0d17865c0d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxesReceivable_f269faf7-0487-4b71-b5c4-908be11c2b8f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeTaxesReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_e4e16bae-a6be-4103-8b5e-7bc03b0ffa02" xlink:to="loc_us-gaap_IncomeTaxesReceivable_f269faf7-0487-4b71-b5c4-908be11c2b8f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherReceivablesNetCurrent_10617524-7f6a-4514-a0fe-2327190707e7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherReceivablesNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_e4e16bae-a6be-4103-8b5e-7bc03b0ffa02" xlink:to="loc_us-gaap_OtherReceivablesNetCurrent_10617524-7f6a-4514-a0fe-2327190707e7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivablesNetCurrent_d9207642-6da7-4815-8274-2366568beb3a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ReceivablesNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_e4e16bae-a6be-4103-8b5e-7bc03b0ffa02" xlink:to="loc_us-gaap_ReceivablesNetCurrent_d9207642-6da7-4815-8274-2366568beb3a" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.westlake.com/role/GoodwillDetails" xlink:type="simple" xlink:href="wlk-20250331.xsd#GoodwillDetails"/>
  <link:definitionLink xlink:role="http://www.westlake.com/role/GoodwillDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillLineItems_c4beff42-3d4d-4811-8310-b554b09af73f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GoodwillLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_d69c3fd3-8992-4e32-9534-f344de2b8de5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfGoodwillTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_c4beff42-3d4d-4811-8310-b554b09af73f" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_d69c3fd3-8992-4e32-9534-f344de2b8de5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_79c512ed-9607-43e7-b3b4-94e5e0792f61" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_d69c3fd3-8992-4e32-9534-f344de2b8de5" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_79c512ed-9607-43e7-b3b4-94e5e0792f61" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_79c512ed-9607-43e7-b3b4-94e5e0792f61_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_79c512ed-9607-43e7-b3b4-94e5e0792f61" xlink:to="loc_us-gaap_SegmentDomain_79c512ed-9607-43e7-b3b4-94e5e0792f61_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_6b37abcf-5aec-4d23-b8c2-9ac8e2341cc9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_79c512ed-9607-43e7-b3b4-94e5e0792f61" xlink:to="loc_us-gaap_SegmentDomain_6b37abcf-5aec-4d23-b8c2-9ac8e2341cc9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_PerformanceAndEssentialMaterialsMember_69149830-118c-4bd3-a67c-21aebeb064f9" xlink:href="wlk-20250331.xsd#wlk_PerformanceAndEssentialMaterialsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_6b37abcf-5aec-4d23-b8c2-9ac8e2341cc9" xlink:to="loc_wlk_PerformanceAndEssentialMaterialsMember_69149830-118c-4bd3-a67c-21aebeb064f9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_HousingAndInfrastructureProductsMember_b47b2744-7295-468a-85c2-4aa9141c5976" xlink:href="wlk-20250331.xsd#wlk_HousingAndInfrastructureProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_6b37abcf-5aec-4d23-b8c2-9ac8e2341cc9" xlink:to="loc_wlk_HousingAndInfrastructureProductsMember_b47b2744-7295-468a-85c2-4aa9141c5976" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillRollForward_1b417a38-e705-4458-9ae7-27ec8e9c5bc3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GoodwillRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_c4beff42-3d4d-4811-8310-b554b09af73f" xlink:to="loc_us-gaap_GoodwillRollForward_1b417a38-e705-4458-9ae7-27ec8e9c5bc3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_c151c74e-e436-4c81-8bbe-129cc0d355d1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_1b417a38-e705-4458-9ae7-27ec8e9c5bc3" xlink:to="loc_us-gaap_Goodwill_c151c74e-e436-4c81-8bbe-129cc0d355d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillForeignCurrencyTranslationGainLoss_139cfda6-e6e0-4436-8d63-ec0f1661207e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GoodwillForeignCurrencyTranslationGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_1b417a38-e705-4458-9ae7-27ec8e9c5bc3" xlink:to="loc_us-gaap_GoodwillForeignCurrencyTranslationGainLoss_139cfda6-e6e0-4436-8d63-ec0f1661207e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_0dfd165b-6511-4cc2-ba73-9f19286b868e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Goodwill"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.westlake.com/role/AccountsPayableDetails" xlink:type="simple" xlink:href="wlk-20250331.xsd#AccountsPayableDetails"/>
  <link:definitionLink xlink:role="http://www.westlake.com/role/AccountsPayableDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_c01c72ac-c985-4630-86fe-b713ad8b9526" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_feca5c21-9f3d-4965-94a2-5d45550108b4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_c01c72ac-c985-4630-86fe-b713ad8b9526" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_feca5c21-9f3d-4965-94a2-5d45550108b4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_9b5f9518-33b4-4133-a525-57c2f5b55b29" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_feca5c21-9f3d-4965-94a2-5d45550108b4" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_9b5f9518-33b4-4133-a525-57c2f5b55b29" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_9b5f9518-33b4-4133-a525-57c2f5b55b29_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_9b5f9518-33b4-4133-a525-57c2f5b55b29" xlink:to="loc_us-gaap_RelatedPartyDomain_9b5f9518-33b4-4133-a525-57c2f5b55b29_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_b4aae0b2-9fbb-4e69-946d-7db3c85c84df" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_9b5f9518-33b4-4133-a525-57c2f5b55b29" xlink:to="loc_us-gaap_RelatedPartyDomain_b4aae0b2-9fbb-4e69-946d-7db3c85c84df" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrelatedPartyMember_9cea1bee-5fa0-4e8f-a897-bdd76a63d4e8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NonrelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_b4aae0b2-9fbb-4e69-946d-7db3c85c84df" xlink:to="loc_us-gaap_NonrelatedPartyMember_9cea1bee-5fa0-4e8f-a897-bdd76a63d4e8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_4756c718-9bdd-4b4f-b236-42613bec1a22" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_b4aae0b2-9fbb-4e69-946d-7db3c85c84df" xlink:to="loc_us-gaap_RelatedPartyMember_4756c718-9bdd-4b4f-b236-42613bec1a22" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableTradeCurrent_7cd115f0-efc9-4c9f-8dc2-7fd9f7945446" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccountsPayableTradeCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_c01c72ac-c985-4630-86fe-b713ad8b9526" xlink:to="loc_us-gaap_AccountsPayableTradeCurrent_7cd115f0-efc9-4c9f-8dc2-7fd9f7945446" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesAndLoansPayableCurrent_94485034-b3d0-4cfc-bfed-11493e4196bc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NotesAndLoansPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_c01c72ac-c985-4630-86fe-b713ad8b9526" xlink:to="loc_us-gaap_NotesAndLoansPayableCurrent_94485034-b3d0-4cfc-bfed-11493e4196bc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_e66f25e4-15eb-435c-9800-5fadded9b852" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_c01c72ac-c985-4630-86fe-b713ad8b9526" xlink:to="loc_us-gaap_AccountsPayableCurrent_e66f25e4-15eb-435c-9800-5fadded9b852" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.westlake.com/role/LongTermDebtScheduleofLongtermDebtDetails" xlink:type="simple" xlink:href="wlk-20250331.xsd#LongTermDebtScheduleofLongtermDebtDetails"/>
  <link:definitionLink xlink:role="http://www.westlake.com/role/LongTermDebtScheduleofLongtermDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_235cb132-17d1-41e7-9394-c3b321cd98e4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_2d60870b-8673-49ea-914e-a1b31844a9bf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_235cb132-17d1-41e7-9394-c3b321cd98e4" xlink:to="loc_us-gaap_DebtInstrumentTable_2d60870b-8673-49ea-914e-a1b31844a9bf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_c8323002-da2a-4648-8735-26ec31a6e2c6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_2d60870b-8673-49ea-914e-a1b31844a9bf" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_c8323002-da2a-4648-8735-26ec31a6e2c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_c8323002-da2a-4648-8735-26ec31a6e2c6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_c8323002-da2a-4648-8735-26ec31a6e2c6" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_c8323002-da2a-4648-8735-26ec31a6e2c6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_2968182b-f6a7-42c3-a608-3de20b5fba57" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_c8323002-da2a-4648-8735-26ec31a6e2c6" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_2968182b-f6a7-42c3-a608-3de20b5fba57" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_bd1b2516-b07f-4806-bb0c-6971980e9808" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_2968182b-f6a7-42c3-a608-3de20b5fba57" xlink:to="loc_us-gaap_SeniorNotesMember_bd1b2516-b07f-4806-bb0c-6971980e9808" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_WasteDisposalRevenueBondsDueTwentyTwentySevenMember_b72d80f1-3000-4095-a0c2-6f3781bb628a" xlink:href="wlk-20250331.xsd#wlk_WasteDisposalRevenueBondsDueTwentyTwentySevenMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_2968182b-f6a7-42c3-a608-3de20b5fba57" xlink:to="loc_wlk_WasteDisposalRevenueBondsDueTwentyTwentySevenMember_b72d80f1-3000-4095-a0c2-6f3781bb628a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_6a12b5d6-41a6-4e21-b121-2fa13c7e5155" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_2d60870b-8673-49ea-914e-a1b31844a9bf" xlink:to="loc_us-gaap_DebtInstrumentAxis_6a12b5d6-41a6-4e21-b121-2fa13c7e5155" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_6a12b5d6-41a6-4e21-b121-2fa13c7e5155_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_6a12b5d6-41a6-4e21-b121-2fa13c7e5155" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_6a12b5d6-41a6-4e21-b121-2fa13c7e5155_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_65b0357d-aff3-47f3-a424-90eefc107328" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_6a12b5d6-41a6-4e21-b121-2fa13c7e5155" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_65b0357d-aff3-47f3-a424-90eefc107328" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_ThreePointSixPercentSeniorNotesDueTwentyTwentySixMember_942f3b69-b897-4a23-9a69-a54594f034fa" xlink:href="wlk-20250331.xsd#wlk_ThreePointSixPercentSeniorNotesDueTwentyTwentySixMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_65b0357d-aff3-47f3-a424-90eefc107328" xlink:to="loc_wlk_ThreePointSixPercentSeniorNotesDueTwentyTwentySixMember_942f3b69-b897-4a23-9a69-a54594f034fa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_WasteDisposalRevenueBondsDueTwentyTwentySevenMember_4d033657-652f-4324-b36d-6e8cc42fa456" xlink:href="wlk-20250331.xsd#wlk_WasteDisposalRevenueBondsDueTwentyTwentySevenMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_65b0357d-aff3-47f3-a424-90eefc107328" xlink:to="loc_wlk_WasteDisposalRevenueBondsDueTwentyTwentySevenMember_4d033657-652f-4324-b36d-6e8cc42fa456" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_OnePointSixTwoFivePercentageSeniorNotesDueTwentyTwentyNineMember_7bdc0b54-b891-443d-ade0-0c6f9d2e2b73" xlink:href="wlk-20250331.xsd#wlk_OnePointSixTwoFivePercentageSeniorNotesDueTwentyTwentyNineMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_65b0357d-aff3-47f3-a424-90eefc107328" xlink:to="loc_wlk_OnePointSixTwoFivePercentageSeniorNotesDueTwentyTwentyNineMember_7bdc0b54-b891-443d-ade0-0c6f9d2e2b73" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_ThreePointThreeSevenFiveSeniorNotesDueTwentyThirtyMember_1a5a5d8e-dea3-41ce-ac19-62b154f8205e" xlink:href="wlk-20250331.xsd#wlk_ThreePointThreeSevenFiveSeniorNotesDueTwentyThirtyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_65b0357d-aff3-47f3-a424-90eefc107328" xlink:to="loc_wlk_ThreePointThreeSevenFiveSeniorNotesDueTwentyThirtyMember_1a5a5d8e-dea3-41ce-ac19-62b154f8205e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_ThreePointFiveZeroPercentSeniorNotesDueTwentyThirtyTwoMember_125123bf-47f5-436b-926d-00722e7c41eb" xlink:href="wlk-20250331.xsd#wlk_ThreePointFiveZeroPercentSeniorNotesDueTwentyThirtyTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_65b0357d-aff3-47f3-a424-90eefc107328" xlink:to="loc_wlk_ThreePointFiveZeroPercentSeniorNotesDueTwentyThirtyTwoMember_125123bf-47f5-436b-926d-00722e7c41eb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_A2875SeniorNotesDue2041Member_86e941a3-3e1a-414d-b716-cf09fef2a25b" xlink:href="wlk-20250331.xsd#wlk_A2875SeniorNotesDue2041Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_65b0357d-aff3-47f3-a424-90eefc107328" xlink:to="loc_wlk_A2875SeniorNotesDue2041Member_86e941a3-3e1a-414d-b716-cf09fef2a25b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_FivePercentSeniorNotesDueTwentyFortySixMember_e5cd5c82-64f8-420e-91cd-38d4c1cd8ea7" xlink:href="wlk-20250331.xsd#wlk_FivePercentSeniorNotesDueTwentyFortySixMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_65b0357d-aff3-47f3-a424-90eefc107328" xlink:to="loc_wlk_FivePercentSeniorNotesDueTwentyFortySixMember_e5cd5c82-64f8-420e-91cd-38d4c1cd8ea7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_FourPointThreeSevenFivePercentSeniorNotesDueTwentyFortySevenMember_79551dc5-12c5-4c3f-86e0-a9f4b0383bc8" xlink:href="wlk-20250331.xsd#wlk_FourPointThreeSevenFivePercentSeniorNotesDueTwentyFortySevenMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_65b0357d-aff3-47f3-a424-90eefc107328" xlink:to="loc_wlk_FourPointThreeSevenFivePercentSeniorNotesDueTwentyFortySevenMember_79551dc5-12c5-4c3f-86e0-a9f4b0383bc8" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_ThreePointOneTwoFivePercentSeniorNotesDueTwentyFiftyOneMember_4a7fb72c-b4d1-4a13-80e2-d98a2dc2c63e" xlink:href="wlk-20250331.xsd#wlk_ThreePointOneTwoFivePercentSeniorNotesDueTwentyFiftyOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_65b0357d-aff3-47f3-a424-90eefc107328" xlink:to="loc_wlk_ThreePointOneTwoFivePercentSeniorNotesDueTwentyFiftyOneMember_4a7fb72c-b4d1-4a13-80e2-d98a2dc2c63e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_ThreePointThreeSevenFivePercentSeniorNotesDueTwentySixtyOneMember_84769de2-f8cc-4e94-8e96-da48332bb44d" xlink:href="wlk-20250331.xsd#wlk_ThreePointThreeSevenFivePercentSeniorNotesDueTwentySixtyOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_65b0357d-aff3-47f3-a424-90eefc107328" xlink:to="loc_wlk_ThreePointThreeSevenFivePercentSeniorNotesDueTwentySixtyOneMember_84769de2-f8cc-4e94-8e96-da48332bb44d" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_TermLoanDueTwentyTwentySixMember_0065ae10-da37-464a-bff5-77c67e8bee7c" xlink:href="wlk-20250331.xsd#wlk_TermLoanDueTwentyTwentySixMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_65b0357d-aff3-47f3-a424-90eefc107328" xlink:to="loc_wlk_TermLoanDueTwentyTwentySixMember_0065ae10-da37-464a-bff5-77c67e8bee7c" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_90146c16-87be-4964-994a-2c8a96b78da3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_235cb132-17d1-41e7-9394-c3b321cd98e4" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_90146c16-87be-4964-994a-2c8a96b78da3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_826047d5-2fb8-4c0c-a626-dbf130fe45dc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_235cb132-17d1-41e7-9394-c3b321cd98e4" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_826047d5-2fb8-4c0c-a626-dbf130fe45dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_4dc6b68d-3dbe-44d3-8cf7-f01ef86296e8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_235cb132-17d1-41e7-9394-c3b321cd98e4" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_4dc6b68d-3dbe-44d3-8cf7-f01ef86296e8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_9b35ca43-07b0-4c0c-8439-4c5a11398845" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_235cb132-17d1-41e7-9394-c3b321cd98e4" xlink:to="loc_us-gaap_LongTermDebt_9b35ca43-07b0-4c0c-8439-4c5a11398845" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_72057890-f1f7-4d57-af4a-2230f0dd7161" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_235cb132-17d1-41e7-9394-c3b321cd98e4" xlink:to="loc_us-gaap_LongTermDebtCurrent_72057890-f1f7-4d57-af4a-2230f0dd7161" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_e5d4389e-2213-4c47-8bae-43145d4122b6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_235cb132-17d1-41e7-9394-c3b321cd98e4" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_e5d4389e-2213-4c47-8bae-43145d4122b6" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.westlake.com/role/LongTermDebtCreditAgreementDetails" xlink:type="simple" xlink:href="wlk-20250331.xsd#LongTermDebtCreditAgreementDetails"/>
  <link:definitionLink xlink:role="http://www.westlake.com/role/LongTermDebtCreditAgreementDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_bbdb46fa-b477-4872-852e-95d5f55e9d58" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_b51f9e97-1106-426e-aa8a-e6ebb4e22fa2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_bbdb46fa-b477-4872-852e-95d5f55e9d58" xlink:to="loc_us-gaap_DebtInstrumentTable_b51f9e97-1106-426e-aa8a-e6ebb4e22fa2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_085688dd-7dec-4225-954a-f557fd7079e0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_b51f9e97-1106-426e-aa8a-e6ebb4e22fa2" xlink:to="loc_us-gaap_DebtInstrumentAxis_085688dd-7dec-4225-954a-f557fd7079e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_085688dd-7dec-4225-954a-f557fd7079e0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_085688dd-7dec-4225-954a-f557fd7079e0" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_085688dd-7dec-4225-954a-f557fd7079e0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_81b48ea2-0927-4279-bc4c-5d4f9730e28c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_085688dd-7dec-4225-954a-f557fd7079e0" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_81b48ea2-0927-4279-bc4c-5d4f9730e28c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_CreditAgreementMember_6a2aa1ab-8b8a-4fef-b3d8-9bbc457d5200" xlink:href="wlk-20250331.xsd#wlk_CreditAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_81b48ea2-0927-4279-bc4c-5d4f9730e28c" xlink:to="loc_wlk_CreditAgreementMember_6a2aa1ab-8b8a-4fef-b3d8-9bbc457d5200" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_c9552519-8fc0-4d4d-b792-425781622199" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_b51f9e97-1106-426e-aa8a-e6ebb4e22fa2" xlink:to="loc_us-gaap_CreditFacilityAxis_c9552519-8fc0-4d4d-b792-425781622199" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_c9552519-8fc0-4d4d-b792-425781622199_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_c9552519-8fc0-4d4d-b792-425781622199" xlink:to="loc_us-gaap_CreditFacilityDomain_c9552519-8fc0-4d4d-b792-425781622199_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_e4b66537-3bb4-4b38-bfd3-a544cfa40e4c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_c9552519-8fc0-4d4d-b792-425781622199" xlink:to="loc_us-gaap_CreditFacilityDomain_e4b66537-3bb4-4b38-bfd3-a544cfa40e4c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_49298945-0e87-448b-9a8b-0a526e938e46" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_e4b66537-3bb4-4b38-bfd3-a544cfa40e4c" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_49298945-0e87-448b-9a8b-0a526e938e46" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_cae07ca9-7375-4ca4-842f-acd892cfe624" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_e4b66537-3bb4-4b38-bfd3-a544cfa40e4c" xlink:to="loc_us-gaap_LetterOfCreditMember_cae07ca9-7375-4ca4-842f-acd892cfe624" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_SwinglineLoanMember_19f04082-306f-4634-bdda-c2b4543a0e60" xlink:href="wlk-20250331.xsd#wlk_SwinglineLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_e4b66537-3bb4-4b38-bfd3-a544cfa40e4c" xlink:to="loc_wlk_SwinglineLoanMember_19f04082-306f-4634-bdda-c2b4543a0e60" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_eb38a481-fb94-4115-ba28-f58ac928f541" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_b51f9e97-1106-426e-aa8a-e6ebb4e22fa2" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_eb38a481-fb94-4115-ba28-f58ac928f541" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_eb38a481-fb94-4115-ba28-f58ac928f541_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_eb38a481-fb94-4115-ba28-f58ac928f541" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_eb38a481-fb94-4115-ba28-f58ac928f541_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_753f1375-6fe7-4ab0-b1e7-fcc493576503" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_eb38a481-fb94-4115-ba28-f58ac928f541" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_753f1375-6fe7-4ab0-b1e7-fcc493576503" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_79921ce9-e0ad-4571-9c5a-4a703463ea24" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_753f1375-6fe7-4ab0-b1e7-fcc493576503" xlink:to="loc_us-gaap_LineOfCreditMember_79921ce9-e0ad-4571-9c5a-4a703463ea24" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_3d4f5b3b-e2a1-46c8-a5ea-fdac849c1762" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_b51f9e97-1106-426e-aa8a-e6ebb4e22fa2" xlink:to="loc_us-gaap_VariableRateAxis_3d4f5b3b-e2a1-46c8-a5ea-fdac849c1762" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_3d4f5b3b-e2a1-46c8-a5ea-fdac849c1762_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_3d4f5b3b-e2a1-46c8-a5ea-fdac849c1762" xlink:to="loc_us-gaap_VariableRateDomain_3d4f5b3b-e2a1-46c8-a5ea-fdac849c1762_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_9c61149e-4cda-45eb-a86b-9d60df6002b0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_3d4f5b3b-e2a1-46c8-a5ea-fdac849c1762" xlink:to="loc_us-gaap_VariableRateDomain_9c61149e-4cda-45eb-a86b-9d60df6002b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredOvernightFinancingRateSofrMember_cb0fce87-6d8f-44ce-a272-860c20f68802" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SecuredOvernightFinancingRateSofrMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_9c61149e-4cda-45eb-a86b-9d60df6002b0" xlink:to="loc_us-gaap_SecuredOvernightFinancingRateSofrMember_cb0fce87-6d8f-44ce-a272-860c20f68802" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_AlternateBaseRateMember_bc3ff452-805c-41b7-a212-55f3354048af" xlink:href="wlk-20250331.xsd#wlk_AlternateBaseRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_9c61149e-4cda-45eb-a86b-9d60df6002b0" xlink:to="loc_wlk_AlternateBaseRateMember_bc3ff452-805c-41b7-a212-55f3354048af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_d3cb2c2c-1d29-4d33-b062-5bc3dfb2a5d2" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_b51f9e97-1106-426e-aa8a-e6ebb4e22fa2" xlink:to="loc_srt_RangeAxis_d3cb2c2c-1d29-4d33-b062-5bc3dfb2a5d2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_d3cb2c2c-1d29-4d33-b062-5bc3dfb2a5d2_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_d3cb2c2c-1d29-4d33-b062-5bc3dfb2a5d2" xlink:to="loc_srt_RangeMember_d3cb2c2c-1d29-4d33-b062-5bc3dfb2a5d2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_68f60862-55cc-4592-9927-db6adf713af8" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_d3cb2c2c-1d29-4d33-b062-5bc3dfb2a5d2" xlink:to="loc_srt_RangeMember_68f60862-55cc-4592-9927-db6adf713af8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_81986851-daed-44e4-b28e-cb4648ea62d1" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_68f60862-55cc-4592-9927-db6adf713af8" xlink:to="loc_srt_MinimumMember_81986851-daed-44e4-b28e-cb4648ea62d1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_a00221b8-6864-4a41-b7f6-deba2e1f8b6e" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_68f60862-55cc-4592-9927-db6adf713af8" xlink:to="loc_srt_MaximumMember_a00221b8-6864-4a41-b7f6-deba2e1f8b6e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_4e99f289-0bd7-4f95-b86a-348a50301218" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_bbdb46fa-b477-4872-852e-95d5f55e9d58" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_4e99f289-0bd7-4f95-b86a-348a50301218" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_7c9517c1-7254-4f13-b178-925341f85584" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_bbdb46fa-b477-4872-852e-95d5f55e9d58" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_7c9517c1-7254-4f13-b178-925341f85584" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_LineOfCreditFacilityPermittedIncrease_3b4f97cf-9749-4bd2-a61b-2c80026d2d2d" xlink:href="wlk-20250331.xsd#wlk_LineOfCreditFacilityPermittedIncrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_bbdb46fa-b477-4872-852e-95d5f55e9d58" xlink:to="loc_wlk_LineOfCreditFacilityPermittedIncrease_3b4f97cf-9749-4bd2-a61b-2c80026d2d2d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding_902162cc-037c-4869-8682-9182c7f0890c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_bbdb46fa-b477-4872-852e-95d5f55e9d58" xlink:to="loc_us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding_902162cc-037c-4869-8682-9182c7f0890c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_7c716de6-87a3-4c9e-9bba-3692646dc123" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_bbdb46fa-b477-4872-852e-95d5f55e9d58" xlink:to="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_7c716de6-87a3-4c9e-9bba-3692646dc123" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.westlake.com/role/AccumulatedOtherComprehensiveIncomeLossScheduleofAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="simple" xlink:href="wlk-20250331.xsd#AccumulatedOtherComprehensiveIncomeLossScheduleofAccumulatedOtherComprehensiveIncomeLossDetails"/>
  <link:definitionLink xlink:role="http://www.westlake.com/role/AccumulatedOtherComprehensiveIncomeLossScheduleofAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_179560af-24e9-4613-8473-f5b53049c064" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_4484af09-dd7d-4859-931a-498a062bd1dc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_179560af-24e9-4613-8473-f5b53049c064" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_4484af09-dd7d-4859-931a-498a062bd1dc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_b2072310-9828-4d64-9837-111bd0b5d042" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_4484af09-dd7d-4859-931a-498a062bd1dc" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_b2072310-9828-4d64-9837-111bd0b5d042" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_b2072310-9828-4d64-9837-111bd0b5d042_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_b2072310-9828-4d64-9837-111bd0b5d042" xlink:to="loc_us-gaap_EquityComponentDomain_b2072310-9828-4d64-9837-111bd0b5d042_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_f4d44a63-62ed-47f2-ba49-01451abe7967" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_b2072310-9828-4d64-9837-111bd0b5d042" xlink:to="loc_us-gaap_EquityComponentDomain_f4d44a63-62ed-47f2-ba49-01451abe7967" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_c30c8268-d2dd-4cf0-9ea4-c5df97c887a6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_f4d44a63-62ed-47f2-ba49-01451abe7967" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_c30c8268-d2dd-4cf0-9ea4-c5df97c887a6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_e65e032d-fbf6-49f9-be99-fa77601e40bb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_c30c8268-d2dd-4cf0-9ea4-c5df97c887a6" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_e65e032d-fbf6-49f9-be99-fa77601e40bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_0ea2179c-2ef5-44b0-abb2-64c80598b24b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_c30c8268-d2dd-4cf0-9ea4-c5df97c887a6" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_0ea2179c-2ef5-44b0-abb2-64c80598b24b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_b877b80b-f074-4a1d-88f2-56b84ec61104" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_179560af-24e9-4613-8473-f5b53049c064" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_b877b80b-f074-4a1d-88f2-56b84ec61104" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_a35a35af-8627-47fe-a940-af31bcad781a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_b877b80b-f074-4a1d-88f2-56b84ec61104" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_a35a35af-8627-47fe-a940-af31bcad781a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_75322930-7d92-4821-829e-31aa6d18df1b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_b877b80b-f074-4a1d-88f2-56b84ec61104" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_75322930-7d92-4821-829e-31aa6d18df1b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_f9087950-f709-49a3-9a92-b42c9ea8c61a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.westlake.com/role/EarningsLossandDividendsperShareAdditionalInformationDetails" xlink:type="simple" xlink:href="wlk-20250331.xsd#EarningsLossandDividendsperShareAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.westlake.com/role/EarningsLossandDividendsperShareAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_13445379-8fe4-4178-9cce-6ff0af02123e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_ea59456e-e394-41d4-bbf2-10f168393b9b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_13445379-8fe4-4178-9cce-6ff0af02123e" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_ea59456e-e394-41d4-bbf2-10f168393b9b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_c261f0af-674b-4b8e-b345-a6664b2c691e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_ea59456e-e394-41d4-bbf2-10f168393b9b" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_c261f0af-674b-4b8e-b345-a6664b2c691e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_c261f0af-674b-4b8e-b345-a6664b2c691e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_c261f0af-674b-4b8e-b345-a6664b2c691e" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_c261f0af-674b-4b8e-b345-a6664b2c691e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_80e045e1-9bbd-42b4-818e-37c848d5b9db" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_c261f0af-674b-4b8e-b345-a6664b2c691e" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_80e045e1-9bbd-42b4-818e-37c848d5b9db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_b4adb4a2-bfbf-42c8-96e4-6de5f4874a1c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_80e045e1-9bbd-42b4-818e-37c848d5b9db" xlink:to="loc_us-gaap_EmployeeStockOptionMember_b4adb4a2-bfbf-42c8-96e4-6de5f4874a1c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_523683cc-21c1-4ba1-9b98-09b01ac59dd5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_80e045e1-9bbd-42b4-818e-37c848d5b9db" xlink:to="loc_us-gaap_PerformanceSharesMember_523683cc-21c1-4ba1-9b98-09b01ac59dd5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_b606366d-8ef7-43e5-84c5-175c16d4745b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_13445379-8fe4-4178-9cce-6ff0af02123e" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_b606366d-8ef7-43e5-84c5-175c16d4745b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.westlake.com/role/SupplementalInformationEquityMethodInvestmentsDetails" xlink:type="simple" xlink:href="wlk-20250331.xsd#SupplementalInformationEquityMethodInvestmentsDetails"/>
  <link:definitionLink xlink:role="http://www.westlake.com/role/SupplementalInformationEquityMethodInvestmentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_27c071e5-8c60-46b6-828f-b9a7b9ee8a54" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_ef532ba7-9341-45ab-b0e6-55a1bc2666a9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_27c071e5-8c60-46b6-828f-b9a7b9ee8a54" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_ef532ba7-9341-45ab-b0e6-55a1bc2666a9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_2bee6d03-1c75-4aa5-9072-9a70ad419cfa" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_ef532ba7-9341-45ab-b0e6-55a1bc2666a9" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_2bee6d03-1c75-4aa5-9072-9a70ad419cfa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_2bee6d03-1c75-4aa5-9072-9a70ad419cfa_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_2bee6d03-1c75-4aa5-9072-9a70ad419cfa" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_2bee6d03-1c75-4aa5-9072-9a70ad419cfa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_08b25a53-96d0-4bde-80aa-e5f4b9707fc8" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_2bee6d03-1c75-4aa5-9072-9a70ad419cfa" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_08b25a53-96d0-4bde-80aa-e5f4b9707fc8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_LACCLLCMember_99685a4b-654a-4f52-838b-f54ba32aff67" xlink:href="wlk-20250331.xsd#wlk_LACCLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_08b25a53-96d0-4bde-80aa-e5f4b9707fc8" xlink:to="loc_wlk_LACCLLCMember_99685a4b-654a-4f52-838b-f54ba32aff67" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_688c5164-bf40-4123-b871-1d9ccd94568a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_27c071e5-8c60-46b6-828f-b9a7b9ee8a54" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_688c5164-bf40-4123-b871-1d9ccd94568a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_EquityMethodInvestmentsActivityRollForward_fd996d5d-fc70-4bd2-bc22-7416cf714632" xlink:href="wlk-20250331.xsd#wlk_EquityMethodInvestmentsActivityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_27c071e5-8c60-46b6-828f-b9a7b9ee8a54" xlink:to="loc_wlk_EquityMethodInvestmentsActivityRollForward_fd996d5d-fc70-4bd2-bc22-7416cf714632" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentOwnedAtFairValue_b1a87a80-a257-4e28-8968-412dd7f418dd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InvestmentOwnedAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_wlk_EquityMethodInvestmentsActivityRollForward_fd996d5d-fc70-4bd2-bc22-7416cf714632" xlink:to="loc_us-gaap_InvestmentOwnedAtFairValue_b1a87a80-a257-4e28-8968-412dd7f418dd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions_6d2d6e69-7fd0-4788-8dcf-2a3de8f67fee" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_wlk_EquityMethodInvestmentsActivityRollForward_fd996d5d-fc70-4bd2-bc22-7416cf714632" xlink:to="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions_6d2d6e69-7fd0-4788-8dcf-2a3de8f67fee" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions_9cb069b6-ceb7-4212-93c9-e14888316e08" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_wlk_EquityMethodInvestmentsActivityRollForward_fd996d5d-fc70-4bd2-bc22-7416cf714632" xlink:to="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions_9cb069b6-ceb7-4212-93c9-e14888316e08" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentOwnedAtFairValue_5a4bca39-f4c3-4365-8cd4-f072c73ff56a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InvestmentOwnedAtFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.westlake.com/role/SupplementalInformationAdditionalInformationDetails" xlink:type="simple" xlink:href="wlk-20250331.xsd#SupplementalInformationAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.westlake.com/role/SupplementalInformationAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_db3b61e6-36f2-46bf-a68e-157009ffc096" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_e292d073-012f-4b25-91e2-9f519f650656" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_db3b61e6-36f2-46bf-a68e-157009ffc096" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_e292d073-012f-4b25-91e2-9f519f650656" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_189ba002-938e-4af0-b16b-0afe52bd069e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_e292d073-012f-4b25-91e2-9f519f650656" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_189ba002-938e-4af0-b16b-0afe52bd069e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_189ba002-938e-4af0-b16b-0afe52bd069e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_189ba002-938e-4af0-b16b-0afe52bd069e" xlink:to="loc_us-gaap_RelatedPartyDomain_189ba002-938e-4af0-b16b-0afe52bd069e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_3b0e86a2-2f77-4f49-9919-126269c654a6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_189ba002-938e-4af0-b16b-0afe52bd069e" xlink:to="loc_us-gaap_RelatedPartyDomain_3b0e86a2-2f77-4f49-9919-126269c654a6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_74c09fac-acda-40ce-86a0-ee30fc9a77e0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_3b0e86a2-2f77-4f49-9919-126269c654a6" xlink:to="loc_us-gaap_RelatedPartyMember_74c09fac-acda-40ce-86a0-ee30fc9a77e0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCostsAndOtherAssets_27991c3e-3db9-49b0-be04-d65cfaefac46" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DeferredCostsAndOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_db3b61e6-36f2-46bf-a68e-157009ffc096" xlink:to="loc_us-gaap_DeferredCostsAndOtherAssets_27991c3e-3db9-49b0-be04-d65cfaefac46" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_DeferredTurnaroundCostsNet_dd08f82e-3337-4283-94a3-5065319c654a" xlink:href="wlk-20250331.xsd#wlk_DeferredTurnaroundCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_db3b61e6-36f2-46bf-a68e-157009ffc096" xlink:to="loc_wlk_DeferredTurnaroundCostsNet_dd08f82e-3337-4283-94a3-5065319c654a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesAndOtherLiabilitiesAbstract_a91bc89d-3b7c-4b3c-95c2-2bfc08bac65e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccruedLiabilitiesAndOtherLiabilitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_db3b61e6-36f2-46bf-a68e-157009ffc096" xlink:to="loc_us-gaap_AccruedLiabilitiesAndOtherLiabilitiesAbstract_a91bc89d-3b7c-4b3c-95c2-2bfc08bac65e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent_ab7a158d-4c3a-4eb4-b40e-0bf84b35cf43" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccruedLiabilitiesAndOtherLiabilitiesAbstract_a91bc89d-3b7c-4b3c-95c2-2bfc08bac65e" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent_ab7a158d-4c3a-4eb4-b40e-0bf84b35cf43" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_AccruedRebatesCurrent_0aa459d4-e253-4575-b20f-77339b2a5c53" xlink:href="wlk-20250331.xsd#wlk_AccruedRebatesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccruedLiabilitiesAndOtherLiabilitiesAbstract_a91bc89d-3b7c-4b3c-95c2-2bfc08bac65e" xlink:to="loc_wlk_AccruedRebatesCurrent_0aa459d4-e253-4575-b20f-77339b2a5c53" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_78487310-2d58-417c-8240-4afa944c6aac" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccruedLiabilitiesAndOtherLiabilitiesAbstract_a91bc89d-3b7c-4b3c-95c2-2bfc08bac65e" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_78487310-2d58-417c-8240-4afa944c6aac" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesCurrent_3836012b-5f37-4a3c-921e-46c5773fa554" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccruedLiabilitiesAndOtherLiabilitiesAbstract_a91bc89d-3b7c-4b3c-95c2-2bfc08bac65e" xlink:to="loc_us-gaap_OtherLiabilitiesCurrent_3836012b-5f37-4a3c-921e-46c5773fa554" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringChargesAbstract_be3d1987-79a7-41a8-89f3-a9082c663560" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringChargesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_db3b61e6-36f2-46bf-a68e-157009ffc096" xlink:to="loc_us-gaap_RestructuringChargesAbstract_be3d1987-79a7-41a8-89f3-a9082c663560" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_78cedabc-672d-48be-8b13-cf152dd35f64" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NoncashInvestingAndFinancingItemsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_db3b61e6-36f2-46bf-a68e-157009ffc096" xlink:to="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_78cedabc-672d-48be-8b13-cf152dd35f64" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_660c0c3f-60ec-4cac-abf2-ad8610542b1d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CapitalExpendituresIncurredButNotYetPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_78cedabc-672d-48be-8b13-cf152dd35f64" xlink:to="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_660c0c3f-60ec-4cac-abf2-ad8610542b1d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIncomeAndExpensesAbstract_ece14829-8786-47ca-a38c-c8987b17a703" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherIncomeAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_db3b61e6-36f2-46bf-a68e-157009ffc096" xlink:to="loc_us-gaap_OtherIncomeAndExpensesAbstract_ece14829-8786-47ca-a38c-c8987b17a703" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_50c4809f-03f7-472a-b882-1eb13b28c03b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_ece14829-8786-47ca-a38c-c8987b17a703" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_50c4809f-03f7-472a-b882-1eb13b28c03b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeOther_cc5d6be6-3ab1-4e80-8f14-5aee7ef85519" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestIncomeOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_ece14829-8786-47ca-a38c-c8987b17a703" xlink:to="loc_us-gaap_InterestIncomeOther_cc5d6be6-3ab1-4e80-8f14-5aee7ef85519" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.westlake.com/role/CommitmentsandContingenciesAdditionalInformationDetails" xlink:type="simple" xlink:href="wlk-20250331.xsd#CommitmentsandContingenciesAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.westlake.com/role/CommitmentsandContingenciesAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_c1de1f21-37fd-4fe1-a754-dc4db67e8457" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_37994ed8-acca-41dd-8914-0dc9948f7ad7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_c1de1f21-37fd-4fe1-a754-dc4db67e8457" xlink:to="loc_us-gaap_LossContingenciesTable_37994ed8-acca-41dd-8914-0dc9948f7ad7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_3093fd54-e07d-4746-84d5-6c200980801d" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_37994ed8-acca-41dd-8914-0dc9948f7ad7" xlink:to="loc_srt_LitigationCaseAxis_3093fd54-e07d-4746-84d5-6c200980801d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_3093fd54-e07d-4746-84d5-6c200980801d_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_3093fd54-e07d-4746-84d5-6c200980801d" xlink:to="loc_srt_LitigationCaseTypeDomain_3093fd54-e07d-4746-84d5-6c200980801d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_b7ebc42b-d9f0-487f-9c3a-d257eb173d65" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_3093fd54-e07d-4746-84d5-6c200980801d" xlink:to="loc_srt_LitigationCaseTypeDomain_b7ebc42b-d9f0-487f-9c3a-d257eb173d65" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_CausticSodaAntitrustProceedingsMember_ad29caaf-adb6-4500-9688-3c2e246408dd" xlink:href="wlk-20250331.xsd#wlk_CausticSodaAntitrustProceedingsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_b7ebc42b-d9f0-487f-9c3a-d257eb173d65" xlink:to="loc_wlk_CausticSodaAntitrustProceedingsMember_ad29caaf-adb6-4500-9688-3c2e246408dd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_EthyleneAntitrustLitigationProceedingsMember_b5e9f047-3f3a-4c5a-9599-612f77c3e5ab" xlink:href="wlk-20250331.xsd#wlk_EthyleneAntitrustLitigationProceedingsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_b7ebc42b-d9f0-487f-9c3a-d257eb173d65" xlink:to="loc_wlk_EthyleneAntitrustLitigationProceedingsMember_b5e9f047-3f3a-4c5a-9599-612f77c3e5ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_TriadHunterProceedingsMember_8583d54b-080c-4573-a564-c913956fc963" xlink:href="wlk-20250331.xsd#wlk_TriadHunterProceedingsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_b7ebc42b-d9f0-487f-9c3a-d257eb173d65" xlink:to="loc_wlk_TriadHunterProceedingsMember_8583d54b-080c-4573-a564-c913956fc963" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_BrazilianContractualIndemnificationLawsuitMember_c9fe9e3e-a7cd-4fab-b02c-38911cec3f46" xlink:href="wlk-20250331.xsd#wlk_BrazilianContractualIndemnificationLawsuitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_b7ebc42b-d9f0-487f-9c3a-d257eb173d65" xlink:to="loc_wlk_BrazilianContractualIndemnificationLawsuitMember_c9fe9e3e-a7cd-4fab-b02c-38911cec3f46" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_SulphurBrineDomeMember_3a75c675-5f68-4548-adba-75b59ee3a6c3" xlink:href="wlk-20250331.xsd#wlk_SulphurBrineDomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_b7ebc42b-d9f0-487f-9c3a-d257eb173d65" xlink:to="loc_wlk_SulphurBrineDomeMember_3a75c675-5f68-4548-adba-75b59ee3a6c3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_LitigationPlaintiffsAxis_cd15ae06-9b11-4a6a-b018-5dbf62fcb1ae" xlink:href="wlk-20250331.xsd#wlk_LitigationPlaintiffsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_37994ed8-acca-41dd-8914-0dc9948f7ad7" xlink:to="loc_wlk_LitigationPlaintiffsAxis_cd15ae06-9b11-4a6a-b018-5dbf62fcb1ae" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_LitigationPlaintiffsDomain_cd15ae06-9b11-4a6a-b018-5dbf62fcb1ae_default" xlink:href="wlk-20250331.xsd#wlk_LitigationPlaintiffsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_wlk_LitigationPlaintiffsAxis_cd15ae06-9b11-4a6a-b018-5dbf62fcb1ae" xlink:to="loc_wlk_LitigationPlaintiffsDomain_cd15ae06-9b11-4a6a-b018-5dbf62fcb1ae_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_LitigationPlaintiffsDomain_2fa25041-85e7-46f6-b424-5ad1097d323f" xlink:href="wlk-20250331.xsd#wlk_LitigationPlaintiffsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_wlk_LitigationPlaintiffsAxis_cd15ae06-9b11-4a6a-b018-5dbf62fcb1ae" xlink:to="loc_wlk_LitigationPlaintiffsDomain_2fa25041-85e7-46f6-b424-5ad1097d323f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_DirectPurchasersMember_d2e21eb9-76b8-47f4-87a8-91473e7666ed" xlink:href="wlk-20250331.xsd#wlk_DirectPurchasersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_wlk_LitigationPlaintiffsDomain_2fa25041-85e7-46f6-b424-5ad1097d323f" xlink:to="loc_wlk_DirectPurchasersMember_d2e21eb9-76b8-47f4-87a8-91473e7666ed" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_IndirectPurchasersMember_cb948afd-cc99-4564-9c47-c4cbfef7c60b" xlink:href="wlk-20250331.xsd#wlk_IndirectPurchasersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_wlk_LitigationPlaintiffsDomain_2fa25041-85e7-46f6-b424-5ad1097d323f" xlink:to="loc_wlk_IndirectPurchasersMember_cb948afd-cc99-4564-9c47-c4cbfef7c60b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_TotalEnergiesPetrochemicalsRefiningSAMember_18c5285c-de90-4343-a65c-5c2883f9435b" xlink:href="wlk-20250331.xsd#wlk_TotalEnergiesPetrochemicalsRefiningSAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_wlk_LitigationPlaintiffsDomain_2fa25041-85e7-46f6-b424-5ad1097d323f" xlink:to="loc_wlk_TotalEnergiesPetrochemicalsRefiningSAMember_18c5285c-de90-4343-a65c-5c2883f9435b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_DowEuropeGmbHDowChemicalIbericaS.L.DowDeutschlandAnlagengesellschaftMbHAndDowBeneluxB.V.Member_c99d9d51-c452-482f-924b-5578ad4130f1" xlink:href="wlk-20250331.xsd#wlk_DowEuropeGmbHDowChemicalIbericaS.L.DowDeutschlandAnlagengesellschaftMbHAndDowBeneluxB.V.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_wlk_LitigationPlaintiffsDomain_2fa25041-85e7-46f6-b424-5ad1097d323f" xlink:to="loc_wlk_DowEuropeGmbHDowChemicalIbericaS.L.DowDeutschlandAnlagengesellschaftMbHAndDowBeneluxB.V.Member_c99d9d51-c452-482f-924b-5578ad4130f1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusAxis_99b420a8-97f7-45e4-bf05-90b1ed9417aa" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LitigationStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_37994ed8-acca-41dd-8914-0dc9948f7ad7" xlink:to="loc_us-gaap_LitigationStatusAxis_99b420a8-97f7-45e4-bf05-90b1ed9417aa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusDomain_99b420a8-97f7-45e4-bf05-90b1ed9417aa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LitigationStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LitigationStatusAxis_99b420a8-97f7-45e4-bf05-90b1ed9417aa" xlink:to="loc_us-gaap_LitigationStatusDomain_99b420a8-97f7-45e4-bf05-90b1ed9417aa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationStatusDomain_a500da43-ce86-4b63-9399-2bbbfc85c872" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LitigationStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LitigationStatusAxis_99b420a8-97f7-45e4-bf05-90b1ed9417aa" xlink:to="loc_us-gaap_LitigationStatusDomain_a500da43-ce86-4b63-9399-2bbbfc85c872" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SettledLitigationMember_f9be396a-d0cf-4dce-853b-c45411bbb27d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SettledLitigationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LitigationStatusDomain_a500da43-ce86-4b63-9399-2bbbfc85c872" xlink:to="loc_us-gaap_SettledLitigationMember_f9be396a-d0cf-4dce-853b-c45411bbb27d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PendingLitigationMember_c1dfc4fd-fde3-4d00-8b48-8a0b8777e06f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PendingLitigationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LitigationStatusDomain_a500da43-ce86-4b63-9399-2bbbfc85c872" xlink:to="loc_us-gaap_PendingLitigationMember_c1dfc4fd-fde3-4d00-8b48-8a0b8777e06f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_0026d978-f95d-4e2c-af95-9b35ba42ddc6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_37994ed8-acca-41dd-8914-0dc9948f7ad7" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_0026d978-f95d-4e2c-af95-9b35ba42ddc6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_0026d978-f95d-4e2c-af95-9b35ba42ddc6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_0026d978-f95d-4e2c-af95-9b35ba42ddc6" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_0026d978-f95d-4e2c-af95-9b35ba42ddc6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_17507751-4a2b-42e1-ba82-f380c7cf4344" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_0026d978-f95d-4e2c-af95-9b35ba42ddc6" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_17507751-4a2b-42e1-ba82-f380c7cf4344" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_8d486ef7-f73a-4419-a849-4f03e721a53a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_17507751-4a2b-42e1-ba82-f380c7cf4344" xlink:to="loc_us-gaap_SubsequentEventMember_8d486ef7-f73a-4419-a849-4f03e721a53a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_3382f39b-3808-4735-b749-a36985f81f77" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_37994ed8-acca-41dd-8914-0dc9948f7ad7" xlink:to="loc_srt_CounterpartyNameAxis_3382f39b-3808-4735-b749-a36985f81f77" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_3382f39b-3808-4735-b749-a36985f81f77_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_3382f39b-3808-4735-b749-a36985f81f77" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_3382f39b-3808-4735-b749-a36985f81f77_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_c5a37a4b-51dd-4932-8251-fd551e6f4c9b" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_3382f39b-3808-4735-b749-a36985f81f77" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_c5a37a4b-51dd-4932-8251-fd551e6f4c9b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_AvientMember_17ee47af-4f25-4f5e-92b9-6224a5a15760" xlink:href="wlk-20250331.xsd#wlk_AvientMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_c5a37a4b-51dd-4932-8251-fd551e6f4c9b" xlink:to="loc_wlk_AvientMember_17ee47af-4f25-4f5e-92b9-6224a5a15760" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EnvironmentalRemediationContingencyAxis_8d343fd9-0ca8-41e4-876b-a691d9832470" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EnvironmentalRemediationContingencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_37994ed8-acca-41dd-8914-0dc9948f7ad7" xlink:to="loc_us-gaap_EnvironmentalRemediationContingencyAxis_8d343fd9-0ca8-41e4-876b-a691d9832470" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EnvironmentalRemediationContingencyDomain_8d343fd9-0ca8-41e4-876b-a691d9832470_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EnvironmentalRemediationContingencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_EnvironmentalRemediationContingencyAxis_8d343fd9-0ca8-41e4-876b-a691d9832470" xlink:to="loc_us-gaap_EnvironmentalRemediationContingencyDomain_8d343fd9-0ca8-41e4-876b-a691d9832470_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EnvironmentalRemediationContingencyDomain_d9217dfc-eda0-4725-a8ea-24ea586cb0ae" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EnvironmentalRemediationContingencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_EnvironmentalRemediationContingencyAxis_8d343fd9-0ca8-41e4-876b-a691d9832470" xlink:to="loc_us-gaap_EnvironmentalRemediationContingencyDomain_d9217dfc-eda0-4725-a8ea-24ea586cb0ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_GroundwaterMonitoringMember_e8c0d03f-ea64-418a-b8c0-676cd573b18b" xlink:href="wlk-20250331.xsd#wlk_GroundwaterMonitoringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EnvironmentalRemediationContingencyDomain_d9217dfc-eda0-4725-a8ea-24ea586cb0ae" xlink:to="loc_wlk_GroundwaterMonitoringMember_e8c0d03f-ea64-418a-b8c0-676cd573b18b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_b52d2534-ac2a-4080-a5f6-6c8e9a844358" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_37994ed8-acca-41dd-8914-0dc9948f7ad7" xlink:to="loc_srt_RangeAxis_b52d2534-ac2a-4080-a5f6-6c8e9a844358" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_b52d2534-ac2a-4080-a5f6-6c8e9a844358_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_b52d2534-ac2a-4080-a5f6-6c8e9a844358" xlink:to="loc_srt_RangeMember_b52d2534-ac2a-4080-a5f6-6c8e9a844358_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_76dc9674-3eae-4ad2-a0ac-22ad3070550d" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_b52d2534-ac2a-4080-a5f6-6c8e9a844358" xlink:to="loc_srt_RangeMember_76dc9674-3eae-4ad2-a0ac-22ad3070550d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_773d5eec-ef38-459f-9182-17e3407f383f" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_76dc9674-3eae-4ad2-a0ac-22ad3070550d" xlink:to="loc_srt_MinimumMember_773d5eec-ef38-459f-9182-17e3407f383f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_90344098-5018-4a46-b329-df019de2c1f0" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_76dc9674-3eae-4ad2-a0ac-22ad3070550d" xlink:to="loc_srt_MaximumMember_90344098-5018-4a46-b329-df019de2c1f0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyDamagesSoughtValue_7a69b190-4d99-4086-86e2-41c513faa9b3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LossContingencyDamagesSoughtValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c1de1f21-37fd-4fe1-a754-dc4db67e8457" xlink:to="loc_us-gaap_LossContingencyDamagesSoughtValue_7a69b190-4d99-4086-86e2-41c513faa9b3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_6dd7e8bc-ee19-4f28-8a72-5ff6bc0f8514" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LitigationSettlementAmountAwardedToOtherParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c1de1f21-37fd-4fe1-a754-dc4db67e8457" xlink:to="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_6dd7e8bc-ee19-4f28-8a72-5ff6bc0f8514" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_LitigationSettlementInterestRate_50da1987-bb2d-4f99-b9b9-aca1f4c80b5f" xlink:href="wlk-20250331.xsd#wlk_LitigationSettlementInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c1de1f21-37fd-4fe1-a754-dc4db67e8457" xlink:to="loc_wlk_LitigationSettlementInterestRate_50da1987-bb2d-4f99-b9b9-aca1f4c80b5f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyAccrualAtCarryingValue_83ff2d05-7763-4c6c-8a3a-0405d937cdf9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LossContingencyAccrualAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c1de1f21-37fd-4fe1-a754-dc4db67e8457" xlink:to="loc_us-gaap_LossContingencyAccrualAtCarryingValue_83ff2d05-7763-4c6c-8a3a-0405d937cdf9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_LitigationSettlementMotionAmountFiledForReliefFromJudgement_fc0c6c2d-709e-44eb-9113-c92827a7225e" xlink:href="wlk-20250331.xsd#wlk_LitigationSettlementMotionAmountFiledForReliefFromJudgement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c1de1f21-37fd-4fe1-a754-dc4db67e8457" xlink:to="loc_wlk_LitigationSettlementMotionAmountFiledForReliefFromJudgement_fc0c6c2d-709e-44eb-9113-c92827a7225e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyDamagesAwardedValue_6678865c-6786-4cc7-83d8-58d416f5a0f6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LossContingencyDamagesAwardedValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c1de1f21-37fd-4fe1-a754-dc4db67e8457" xlink:to="loc_us-gaap_LossContingencyDamagesAwardedValue_6678865c-6786-4cc7-83d8-58d416f5a0f6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_LitigationSettlementLegalFeeAndProceduralFinePercentage_7b5d7d73-e0f1-447e-809c-9e6a35f7d969" xlink:href="wlk-20250331.xsd#wlk_LitigationSettlementLegalFeeAndProceduralFinePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c1de1f21-37fd-4fe1-a754-dc4db67e8457" xlink:to="loc_wlk_LitigationSettlementLegalFeeAndProceduralFinePercentage_7b5d7d73-e0f1-447e-809c-9e6a35f7d969" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EnvironmentalExitCostsAnticipatedCost_df66a2b4-eeb9-474e-8f31-776b39864b64" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EnvironmentalExitCostsAnticipatedCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c1de1f21-37fd-4fe1-a754-dc4db67e8457" xlink:to="loc_us-gaap_EnvironmentalExitCostsAnticipatedCost_df66a2b4-eeb9-474e-8f31-776b39864b64" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EnvironmentalExitCostsReasonablyPossibleAdditionalLoss_c38217e3-0b15-418c-8d21-427348d629cd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EnvironmentalExitCostsReasonablyPossibleAdditionalLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c1de1f21-37fd-4fe1-a754-dc4db67e8457" xlink:to="loc_us-gaap_EnvironmentalExitCostsReasonablyPossibleAdditionalLoss_c38217e3-0b15-418c-8d21-427348d629cd" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.westlake.com/role/SegmentInformationSegmentReportingInformationDetails" xlink:type="simple" xlink:href="wlk-20250331.xsd#SegmentInformationSegmentReportingInformationDetails"/>
  <link:definitionLink xlink:role="http://www.westlake.com/role/SegmentInformationSegmentReportingInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_db72ad4e-5c6e-48bc-b5a5-b5d186ffcab0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_5f7fe80b-2f79-4379-a701-22c9fd492c59" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_db72ad4e-5c6e-48bc-b5a5-b5d186ffcab0" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_5f7fe80b-2f79-4379-a701-22c9fd492c59" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_225ccd73-e0a2-408e-962f-47058ebbc036" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_5f7fe80b-2f79-4379-a701-22c9fd492c59" xlink:to="loc_srt_ConsolidationItemsAxis_225ccd73-e0a2-408e-962f-47058ebbc036" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_225ccd73-e0a2-408e-962f-47058ebbc036_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_225ccd73-e0a2-408e-962f-47058ebbc036" xlink:to="loc_srt_ConsolidationItemsDomain_225ccd73-e0a2-408e-962f-47058ebbc036_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_27536887-9dc6-4693-b19f-32ddc254ecbc" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_225ccd73-e0a2-408e-962f-47058ebbc036" xlink:to="loc_srt_ConsolidationItemsDomain_27536887-9dc6-4693-b19f-32ddc254ecbc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_2e5d730d-401f-477f-a383-2401bfb0c7e4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_27536887-9dc6-4693-b19f-32ddc254ecbc" xlink:to="loc_us-gaap_OperatingSegmentsMember_2e5d730d-401f-477f-a383-2401bfb0c7e4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntersegmentEliminationMember_3a901427-0462-46f9-ba89-4c6032061bb6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IntersegmentEliminationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_27536887-9dc6-4693-b19f-32ddc254ecbc" xlink:to="loc_us-gaap_IntersegmentEliminationMember_3a901427-0462-46f9-ba89-4c6032061bb6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_a873bfde-eec1-45e8-8a64-24c04530b396" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_27536887-9dc6-4693-b19f-32ddc254ecbc" xlink:to="loc_us-gaap_CorporateNonSegmentMember_a873bfde-eec1-45e8-8a64-24c04530b396" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_fd195838-5e53-40f9-9914-8303e77d05a0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_5f7fe80b-2f79-4379-a701-22c9fd492c59" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_fd195838-5e53-40f9-9914-8303e77d05a0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_fd195838-5e53-40f9-9914-8303e77d05a0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_fd195838-5e53-40f9-9914-8303e77d05a0" xlink:to="loc_us-gaap_SegmentDomain_fd195838-5e53-40f9-9914-8303e77d05a0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_5c5b2acd-e536-427a-88f7-0c78d4291659" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_fd195838-5e53-40f9-9914-8303e77d05a0" xlink:to="loc_us-gaap_SegmentDomain_5c5b2acd-e536-427a-88f7-0c78d4291659" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_PerformanceAndEssentialMaterialsMember_548ff0f3-05b8-4035-9fbd-d8900b6a04b5" xlink:href="wlk-20250331.xsd#wlk_PerformanceAndEssentialMaterialsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_5c5b2acd-e536-427a-88f7-0c78d4291659" xlink:to="loc_wlk_PerformanceAndEssentialMaterialsMember_548ff0f3-05b8-4035-9fbd-d8900b6a04b5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_HousingAndInfrastructureProductsMember_5f3dc5ae-d9de-43bf-9994-06a2f9fc0068" xlink:href="wlk-20250331.xsd#wlk_HousingAndInfrastructureProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_5c5b2acd-e536-427a-88f7-0c78d4291659" xlink:to="loc_wlk_HousingAndInfrastructureProductsMember_5f3dc5ae-d9de-43bf-9994-06a2f9fc0068" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_e0e9703f-5b41-472d-8d50-c008c1e1114c" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_5f7fe80b-2f79-4379-a701-22c9fd492c59" xlink:to="loc_srt_ProductOrServiceAxis_e0e9703f-5b41-472d-8d50-c008c1e1114c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_e0e9703f-5b41-472d-8d50-c008c1e1114c_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_e0e9703f-5b41-472d-8d50-c008c1e1114c" xlink:to="loc_srt_ProductsAndServicesDomain_e0e9703f-5b41-472d-8d50-c008c1e1114c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_55b4fbd2-ae56-45f1-9e48-a215a96af83d" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_e0e9703f-5b41-472d-8d50-c008c1e1114c" xlink:to="loc_srt_ProductsAndServicesDomain_55b4fbd2-ae56-45f1-9e48-a215a96af83d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_PerformanceMaterialsMember_c05c3e0b-c0fb-4a0f-8650-e1147ba99133" xlink:href="wlk-20250331.xsd#wlk_PerformanceMaterialsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_55b4fbd2-ae56-45f1-9e48-a215a96af83d" xlink:to="loc_wlk_PerformanceMaterialsMember_c05c3e0b-c0fb-4a0f-8650-e1147ba99133" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_EssentialMaterialsMember_dbba2b56-ccc3-4e94-bb01-cd876cb0e96f" xlink:href="wlk-20250331.xsd#wlk_EssentialMaterialsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_55b4fbd2-ae56-45f1-9e48-a215a96af83d" xlink:to="loc_wlk_EssentialMaterialsMember_dbba2b56-ccc3-4e94-bb01-cd876cb0e96f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_HousingProductsMember_e280cdb7-7d63-491d-b46e-2e82136bb152" xlink:href="wlk-20250331.xsd#wlk_HousingProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_55b4fbd2-ae56-45f1-9e48-a215a96af83d" xlink:to="loc_wlk_HousingProductsMember_e280cdb7-7d63-491d-b46e-2e82136bb152" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_InfrastructureProductsMember_349815b0-04c9-4cf4-8052-d1da9a6eb279" xlink:href="wlk-20250331.xsd#wlk_InfrastructureProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_55b4fbd2-ae56-45f1-9e48-a215a96af83d" xlink:to="loc_wlk_InfrastructureProductsMember_349815b0-04c9-4cf4-8052-d1da9a6eb279" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_6ef55d72-1768-419f-b2b8-fee31b027461" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_db72ad4e-5c6e-48bc-b5a5-b5d186ffcab0" xlink:to="loc_us-gaap_Revenues_6ef55d72-1768-419f-b2b8-fee31b027461" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_RawMaterialEnergyAndManufacturingCosts_fe2b3e71-2caa-467a-a0a9-5337036a3e36" xlink:href="wlk-20250331.xsd#wlk_RawMaterialEnergyAndManufacturingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_db72ad4e-5c6e-48bc-b5a5-b5d186ffcab0" xlink:to="loc_wlk_RawMaterialEnergyAndManufacturingCosts_fe2b3e71-2caa-467a-a0a9-5337036a3e36" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_DepreciationAndAmortizationSegmentExpenses_f9482bf6-ac77-4966-a7dc-d837e9023a11" xlink:href="wlk-20250331.xsd#wlk_DepreciationAndAmortizationSegmentExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_db72ad4e-5c6e-48bc-b5a5-b5d186ffcab0" xlink:to="loc_wlk_DepreciationAndAmortizationSegmentExpenses_f9482bf6-ac77-4966-a7dc-d837e9023a11" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_1a016033-0d14-4fe3-a51e-91a05b5d145b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_db72ad4e-5c6e-48bc-b5a5-b5d186ffcab0" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_1a016033-0d14-4fe3-a51e-91a05b5d145b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_SellingGeneralAndAdministrativeExpenses_7ba5e05d-0e54-4fac-b7b3-b5d9b49b3be3" xlink:href="wlk-20250331.xsd#wlk_SellingGeneralAndAdministrativeExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_db72ad4e-5c6e-48bc-b5a5-b5d186ffcab0" xlink:to="loc_wlk_SellingGeneralAndAdministrativeExpenses_7ba5e05d-0e54-4fac-b7b3-b5d9b49b3be3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_DepreciationAndAmortizationSGA_3e00d777-168b-4dd7-b2f6-cd2b398eb1ff" xlink:href="wlk-20250331.xsd#wlk_DepreciationAndAmortizationSGA"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_db72ad4e-5c6e-48bc-b5a5-b5d186ffcab0" xlink:to="loc_wlk_DepreciationAndAmortizationSGA_3e00d777-168b-4dd7-b2f6-cd2b398eb1ff" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_RestructuringTransactionAndIntegrationRelatedCosts_ded12250-a42e-4cf6-8add-cf46bb3ddf6c" xlink:href="wlk-20250331.xsd#wlk_RestructuringTransactionAndIntegrationRelatedCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_db72ad4e-5c6e-48bc-b5a5-b5d186ffcab0" xlink:to="loc_wlk_RestructuringTransactionAndIntegrationRelatedCosts_ded12250-a42e-4cf6-8add-cf46bb3ddf6c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_TotalSellingGeneralAndAdministrativeExpenses_8ae2a8f8-29e4-4f0c-90d7-247078f76dbe" xlink:href="wlk-20250331.xsd#wlk_TotalSellingGeneralAndAdministrativeExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_db72ad4e-5c6e-48bc-b5a5-b5d186ffcab0" xlink:to="loc_wlk_TotalSellingGeneralAndAdministrativeExpenses_8ae2a8f8-29e4-4f0c-90d7-247078f76dbe" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_db8d20c8-db9e-433c-9882-59721d698288" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_db72ad4e-5c6e-48bc-b5a5-b5d186ffcab0" xlink:to="loc_us-gaap_OperatingIncomeLoss_db8d20c8-db9e-433c-9882-59721d698288" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_3da938b1-27a8-40b1-8355-b5d0a337bdbb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_db72ad4e-5c6e-48bc-b5a5-b5d186ffcab0" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_3da938b1-27a8-40b1-8355-b5d0a337bdbb" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_1cf1b50a-c361-4576-80b5-ef69607df639" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_db72ad4e-5c6e-48bc-b5a5-b5d186ffcab0" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_1cf1b50a-c361-4576-80b5-ef69607df639" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_cb2f8eee-61e7-4843-aaa9-8879e71d9cf8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_db72ad4e-5c6e-48bc-b5a5-b5d186ffcab0" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_cb2f8eee-61e7-4843-aaa9-8879e71d9cf8" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentExpenditureAdditionToLongLivedAssets_98dfa3c0-40c4-43b8-b467-8672e3cc9bcf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentExpenditureAdditionToLongLivedAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_db72ad4e-5c6e-48bc-b5a5-b5d186ffcab0" xlink:to="loc_us-gaap_SegmentExpenditureAdditionToLongLivedAssets_98dfa3c0-40c4-43b8-b467-8672e3cc9bcf" xlink:type="arc" order="12"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.westlake.com/role/SegmentInformationReconciliationofTotalSegmentIncomefromOperationstoConsolidatedIncomebeforeIncomeTaxesDetails" xlink:type="simple" xlink:href="wlk-20250331.xsd#SegmentInformationReconciliationofTotalSegmentIncomefromOperationstoConsolidatedIncomebeforeIncomeTaxesDetails"/>
  <link:definitionLink xlink:role="http://www.westlake.com/role/SegmentInformationReconciliationofTotalSegmentIncomefromOperationstoConsolidatedIncomebeforeIncomeTaxesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_3dc11cfd-87b0-4b39-8270-2480931481a0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_8c571dd2-3b7f-4fa6-a26b-d4a7ceab578a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3dc11cfd-87b0-4b39-8270-2480931481a0" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_8c571dd2-3b7f-4fa6-a26b-d4a7ceab578a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_ba5259f1-d39a-4ea0-8e23-588ff08c4dfc" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_8c571dd2-3b7f-4fa6-a26b-d4a7ceab578a" xlink:to="loc_srt_ConsolidationItemsAxis_ba5259f1-d39a-4ea0-8e23-588ff08c4dfc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_ba5259f1-d39a-4ea0-8e23-588ff08c4dfc_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_ba5259f1-d39a-4ea0-8e23-588ff08c4dfc" xlink:to="loc_srt_ConsolidationItemsDomain_ba5259f1-d39a-4ea0-8e23-588ff08c4dfc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_a228cbb6-40e3-4362-b071-df53eacecb1e" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_ba5259f1-d39a-4ea0-8e23-588ff08c4dfc" xlink:to="loc_srt_ConsolidationItemsDomain_a228cbb6-40e3-4362-b071-df53eacecb1e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_684d1978-1cb8-4dc1-b442-a6b83cd79719" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_a228cbb6-40e3-4362-b071-df53eacecb1e" xlink:to="loc_us-gaap_OperatingSegmentsMember_684d1978-1cb8-4dc1-b442-a6b83cd79719" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_a1c7e2e3-4914-450f-a244-1d914d0abdf1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_a228cbb6-40e3-4362-b071-df53eacecb1e" xlink:to="loc_us-gaap_CorporateNonSegmentMember_a1c7e2e3-4914-450f-a244-1d914d0abdf1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_cc4d3bef-c0bd-41ee-8543-75dae06f8e10" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3dc11cfd-87b0-4b39-8270-2480931481a0" xlink:to="loc_us-gaap_OperatingIncomeLoss_cc4d3bef-c0bd-41ee-8543-75dae06f8e10" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseNonoperating_d0783ca3-4c2c-48d5-a613-1ac2aac56257" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestExpenseNonoperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3dc11cfd-87b0-4b39-8270-2480931481a0" xlink:to="loc_us-gaap_InterestExpenseNonoperating_d0783ca3-4c2c-48d5-a613-1ac2aac56257" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_b3ac0046-efee-4895-a52b-8a579f6ca507" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3dc11cfd-87b0-4b39-8270-2480931481a0" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_b3ac0046-efee-4895-a52b-8a579f6ca507" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_9b7d627a-8919-4fa9-a8c9-fd60c6f38c22" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3dc11cfd-87b0-4b39-8270-2480931481a0" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_9b7d627a-8919-4fa9-a8c9-fd60c6f38c22" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.westlake.com/role/SegmentInformationTotalAssetsDetails" xlink:type="simple" xlink:href="wlk-20250331.xsd#SegmentInformationTotalAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.westlake.com/role/SegmentInformationTotalAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_c2e74281-3a10-4782-a3b5-a005a6559ec6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentReportingAssetReconcilingItemLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReconciliationOfAssetsFromSegmentToConsolidatedTable_126fad5a-8204-426e-9989-11e0add21ae1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ReconciliationOfAssetsFromSegmentToConsolidatedTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_c2e74281-3a10-4782-a3b5-a005a6559ec6" xlink:to="loc_us-gaap_ReconciliationOfAssetsFromSegmentToConsolidatedTable_126fad5a-8204-426e-9989-11e0add21ae1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_d4fdbfba-1d93-4d19-a0c7-70e9317e9f9b" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReconciliationOfAssetsFromSegmentToConsolidatedTable_126fad5a-8204-426e-9989-11e0add21ae1" xlink:to="loc_srt_ConsolidationItemsAxis_d4fdbfba-1d93-4d19-a0c7-70e9317e9f9b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_d4fdbfba-1d93-4d19-a0c7-70e9317e9f9b_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_d4fdbfba-1d93-4d19-a0c7-70e9317e9f9b" xlink:to="loc_srt_ConsolidationItemsDomain_d4fdbfba-1d93-4d19-a0c7-70e9317e9f9b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_cbd96314-f378-47e3-8b9b-f609939b7162" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_d4fdbfba-1d93-4d19-a0c7-70e9317e9f9b" xlink:to="loc_srt_ConsolidationItemsDomain_cbd96314-f378-47e3-8b9b-f609939b7162" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_37f11aae-4cf4-493f-8186-bf6e3b11c001" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_cbd96314-f378-47e3-8b9b-f609939b7162" xlink:to="loc_us-gaap_OperatingSegmentsMember_37f11aae-4cf4-493f-8186-bf6e3b11c001" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_277f8dd1-df71-4333-9c47-4b71b18babda" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_cbd96314-f378-47e3-8b9b-f609939b7162" xlink:to="loc_us-gaap_CorporateNonSegmentMember_277f8dd1-df71-4333-9c47-4b71b18babda" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_79219bb5-97ef-4440-bd24-46d29ab1f144" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReconciliationOfAssetsFromSegmentToConsolidatedTable_126fad5a-8204-426e-9989-11e0add21ae1" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_79219bb5-97ef-4440-bd24-46d29ab1f144" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_79219bb5-97ef-4440-bd24-46d29ab1f144_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_79219bb5-97ef-4440-bd24-46d29ab1f144" xlink:to="loc_us-gaap_SegmentDomain_79219bb5-97ef-4440-bd24-46d29ab1f144_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_57f98487-07aa-45a1-a705-296abd0bad19" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_79219bb5-97ef-4440-bd24-46d29ab1f144" xlink:to="loc_us-gaap_SegmentDomain_57f98487-07aa-45a1-a705-296abd0bad19" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_PerformanceAndEssentialMaterialsMember_40fadd06-26b3-4ab5-b87d-09f1687feb3d" xlink:href="wlk-20250331.xsd#wlk_PerformanceAndEssentialMaterialsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_57f98487-07aa-45a1-a705-296abd0bad19" xlink:to="loc_wlk_PerformanceAndEssentialMaterialsMember_40fadd06-26b3-4ab5-b87d-09f1687feb3d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_HousingAndInfrastructureProductsMember_53e9ca0d-9e67-45f9-8d79-96578e76a4ae" xlink:href="wlk-20250331.xsd#wlk_HousingAndInfrastructureProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_57f98487-07aa-45a1-a705-296abd0bad19" xlink:to="loc_wlk_HousingAndInfrastructureProductsMember_53e9ca0d-9e67-45f9-8d79-96578e76a4ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_6c2fac2f-1495-461b-ba24-e0c1d3cb8c39" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_c2e74281-3a10-4782-a3b5-a005a6559ec6" xlink:to="loc_us-gaap_Assets_6c2fac2f-1495-461b-ba24-e0c1d3cb8c39" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_666147f7-8e91-44d0-81a4-4a8bc211bff3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_c2e74281-3a10-4782-a3b5-a005a6559ec6" xlink:to="loc_us-gaap_EquityMethodInvestments_666147f7-8e91-44d0-81a4-4a8bc211bff3" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.westlake.com/role/WestlakeChemicalPartnersLPDetails" xlink:type="simple" xlink:href="wlk-20250331.xsd#WestlakeChemicalPartnersLPDetails"/>
  <link:definitionLink xlink:role="http://www.westlake.com/role/WestlakeChemicalPartnersLPDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_1dd520f9-4386-4a35-945e-f501887db45c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_7556fd68-bb7b-4a50-9843-398b2c8cd0e5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1dd520f9-4386-4a35-945e-f501887db45c" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_7556fd68-bb7b-4a50-9843-398b2c8cd0e5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3d63a018-62f2-4d52-b6c6-ac3a4e3f28bd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_7556fd68-bb7b-4a50-9843-398b2c8cd0e5" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3d63a018-62f2-4d52-b6c6-ac3a4e3f28bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_3d63a018-62f2-4d52-b6c6-ac3a4e3f28bd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3d63a018-62f2-4d52-b6c6-ac3a4e3f28bd" xlink:to="loc_us-gaap_RelatedPartyDomain_3d63a018-62f2-4d52-b6c6-ac3a4e3f28bd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_12bc6782-3c3c-45cf-acae-5fa52083f5b1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3d63a018-62f2-4d52-b6c6-ac3a4e3f28bd" xlink:to="loc_us-gaap_RelatedPartyDomain_12bc6782-3c3c-45cf-acae-5fa52083f5b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiaryOfCommonParentMember_245588cb-d32b-478e-80c0-4da637683f0d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsidiaryOfCommonParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_12bc6782-3c3c-45cf-acae-5fa52083f5b1" xlink:to="loc_us-gaap_SubsidiaryOfCommonParentMember_245588cb-d32b-478e-80c0-4da637683f0d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_a858599b-d66c-4efe-98e2-dc2e61d02517" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_7556fd68-bb7b-4a50-9843-398b2c8cd0e5" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_a858599b-d66c-4efe-98e2-dc2e61d02517" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_a858599b-d66c-4efe-98e2-dc2e61d02517_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_a858599b-d66c-4efe-98e2-dc2e61d02517" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_a858599b-d66c-4efe-98e2-dc2e61d02517_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_286cdcc1-3a4f-4a40-a007-2dc5e2e2b51a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_a858599b-d66c-4efe-98e2-dc2e61d02517" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_286cdcc1-3a4f-4a40-a007-2dc5e2e2b51a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnerMember_513b0c18-994a-422c-ae1f-0f8453ed04d1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LimitedPartnerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_286cdcc1-3a4f-4a40-a007-2dc5e2e2b51a" xlink:to="loc_us-gaap_LimitedPartnerMember_513b0c18-994a-422c-ae1f-0f8453ed04d1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_b7131330-c00d-410b-8d06-611d67929766" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_7556fd68-bb7b-4a50-9843-398b2c8cd0e5" xlink:to="loc_srt_OwnershipAxis_b7131330-c00d-410b-8d06-611d67929766" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_b7131330-c00d-410b-8d06-611d67929766_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_b7131330-c00d-410b-8d06-611d67929766" xlink:to="loc_srt_OwnershipDomain_b7131330-c00d-410b-8d06-611d67929766_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_83d5a632-3e75-4338-89e8-eaf7e9f5ee73" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_b7131330-c00d-410b-8d06-611d67929766" xlink:to="loc_srt_OwnershipDomain_83d5a632-3e75-4338-89e8-eaf7e9f5ee73" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_WestlakeChemicalOpCoLPMember_67bbbfc1-dbce-4deb-960d-5936745fe7cf" xlink:href="wlk-20250331.xsd#wlk_WestlakeChemicalOpCoLPMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_83d5a632-3e75-4338-89e8-eaf7e9f5ee73" xlink:to="loc_wlk_WestlakeChemicalOpCoLPMember_67bbbfc1-dbce-4deb-960d-5936745fe7cf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_WestlakeChemicalPartnersLPMember_14f6e1c6-0dbe-4973-a0fa-2be8b7dfd9c2" xlink:href="wlk-20250331.xsd#wlk_WestlakeChemicalPartnersLPMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_83d5a632-3e75-4338-89e8-eaf7e9f5ee73" xlink:to="loc_wlk_WestlakeChemicalPartnersLPMember_14f6e1c6-0dbe-4973-a0fa-2be8b7dfd9c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAccountUnitsSoldInPublicOffering_0fe9306e-4969-4709-9ac8-00af60a02885" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PartnersCapitalAccountUnitsSoldInPublicOffering"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1dd520f9-4386-4a35-945e-f501887db45c" xlink:to="loc_us-gaap_PartnersCapitalAccountUnitsSoldInPublicOffering_0fe9306e-4969-4709-9ac8-00af60a02885" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPManagingMemberOrGeneralPartnerOwnershipInterest_1d4c0833-7fd1-4ec5-ac4d-e80dc298ea46" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPManagingMemberOrGeneralPartnerOwnershipInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1dd520f9-4386-4a35-945e-f501887db45c" xlink:to="loc_us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPManagingMemberOrGeneralPartnerOwnershipInterest_1d4c0833-7fd1-4ec5-ac4d-e80dc298ea46" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest_1919b265-1b1f-4796-a97f-a095e427012c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1dd520f9-4386-4a35-945e-f501887db45c" xlink:to="loc_us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest_1919b265-1b1f-4796-a97f-a095e427012c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAccountUnits_5e684968-32c9-47ea-9c7b-cc4bb82b6714" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PartnersCapitalAccountUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1dd520f9-4386-4a35-945e-f501887db45c" xlink:to="loc_us-gaap_PartnersCapitalAccountUnits_5e684968-32c9-47ea-9c7b-cc4bb82b6714" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_wlk_PartnersUnitsMaximumAggregateOfferingAmountATM_c0754639-3943-44eb-970e-d529dbc72932" xlink:href="wlk-20250331.xsd#wlk_PartnersUnitsMaximumAggregateOfferingAmountATM"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_1dd520f9-4386-4a35-945e-f501887db45c" xlink:to="loc_wlk_PartnersUnitsMaximumAggregateOfferingAmountATM_c0754639-3943-44eb-970e-d529dbc72932" xlink:type="arc" order="4"/>
  </link:definitionLink>
</link:linkbase>
