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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019e40ee-aeb4-7b37-9fca-6caafa6d4153,g:e84d7749-ab0b-4a6b-bdfb-93e99fc44371-->
<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.qnityelectronics.com/role/ConsolidatedStatementsofChangesinEquityUnaudited" xlink:type="simple" xlink:href="q-20260630.xsd#ConsolidatedStatementsofChangesinEquityUnaudited"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/ConsolidatedStatementsofChangesinEquityUnaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019e40ee-b039-7093-a356-4e900b39268e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019e40ee-b039-7c1d-9fd7-96ce2ccd182d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019e40ee-b039-7093-a356-4e900b39268e" xlink:to="loc_us-gaap_StatementTable_019e40ee-b039-7c1d-9fd7-96ce2ccd182d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019e40ee-b039-77e3-a179-3df2c848352e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e40ee-b039-7c1d-9fd7-96ce2ccd182d" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019e40ee-b039-77e3-a179-3df2c848352e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019e40ee-b039-77e3-a179-3df2c848352e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019e40ee-b039-77e3-a179-3df2c848352e" xlink:to="loc_us-gaap_EquityComponentDomain_019e40ee-b039-77e3-a179-3df2c848352e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019e40ee-b039-7ff2-b0d6-a6ac2c238d56" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019e40ee-b039-77e3-a179-3df2c848352e" xlink:to="loc_us-gaap_EquityComponentDomain_019e40ee-b039-7ff2-b0d6-a6ac2c238d56" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019e40ee-b039-7da9-bfb9-2321aae0e6de" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e40ee-b039-7ff2-b0d6-a6ac2c238d56" xlink:to="loc_us-gaap_CommonStockMember_019e40ee-b039-7da9-bfb9-2321aae0e6de" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockMember_019e40ee-b039-78f8-810a-7e015c59dfd3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e40ee-b039-7ff2-b0d6-a6ac2c238d56" xlink:to="loc_us-gaap_PreferredStockMember_019e40ee-b039-78f8-810a-7e015c59dfd3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_019e40ee-b039-7a67-a68f-9f6dfff5fa23" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e40ee-b039-7ff2-b0d6-a6ac2c238d56" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_019e40ee-b039-7a67-a68f-9f6dfff5fa23" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_019e40ee-b039-76d7-b041-54a9d63b1231" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e40ee-b039-7ff2-b0d6-a6ac2c238d56" xlink:to="loc_us-gaap_RetainedEarningsMember_019e40ee-b039-76d7-b041-54a9d63b1231" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_ParentCompanyNetInvestmentMember_019e40ee-b039-78d9-af4b-28ddab59cee5" xlink:href="q-20260630.xsd#q_ParentCompanyNetInvestmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e40ee-b039-7ff2-b0d6-a6ac2c238d56" xlink:to="loc_q_ParentCompanyNetInvestmentMember_019e40ee-b039-78d9-af4b-28ddab59cee5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019e40ee-b039-7078-9486-64cd017747d2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e40ee-b039-7ff2-b0d6-a6ac2c238d56" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019e40ee-b039-7078-9486-64cd017747d2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_019e40ee-b039-7c3c-b27d-8d505ba75909" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e40ee-b039-7ff2-b0d6-a6ac2c238d56" xlink:to="loc_us-gaap_NoncontrollingInterestMember_019e40ee-b039-7c3c-b27d-8d505ba75909" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e40ee-b039-7ed3-80bd-b7f7599fcaf0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e40ee-b039-7093-a356-4e900b39268e" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e40ee-b039-7ed3-80bd-b7f7599fcaf0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019e40ee-b039-70bb-9622-1604b37cab8b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e40ee-b039-7ed3-80bd-b7f7599fcaf0" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019e40ee-b039-70bb-9622-1604b37cab8b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019e40ee-b039-7c7e-a394-59a5dd407fc0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e40ee-b039-7ed3-80bd-b7f7599fcaf0" xlink:to="loc_us-gaap_ProfitLoss_019e40ee-b039-7c7e-a394-59a5dd407fc0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019e40ee-b039-7d52-ab0e-40c69084174c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e40ee-b039-7ed3-80bd-b7f7599fcaf0" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019e40ee-b039-7d52-ab0e-40c69084174c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_019e40ee-b039-7856-b1ed-b03ca0747116" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e40ee-b039-7ed3-80bd-b7f7599fcaf0" xlink:to="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_019e40ee-b039-7856-b1ed-b03ca0747116" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_TransferToParentCompany_019e40ee-b039-7284-ad7e-d6461443d2fe" xlink:href="q-20260630.xsd#q_TransferToParentCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e40ee-b039-7ed3-80bd-b7f7599fcaf0" xlink:to="loc_q_TransferToParentCompany_019e40ee-b039-7284-ad7e-d6461443d2fe" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Dividends_019f8365-da44-7ea0-b648-2f22926fefdd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Dividends"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e40ee-b039-7ed3-80bd-b7f7599fcaf0" xlink:to="loc_us-gaap_Dividends_019f8365-da44-7ea0-b648-2f22926fefdd" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019e40ee-b039-7e82-960c-ca3f78569ff2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e40ee-b039-7ed3-80bd-b7f7599fcaf0" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019e40ee-b039-7e82-960c-ca3f78569ff2" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_019e40ee-b039-7526-9e09-696e3bc66c3e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e40ee-b039-7ed3-80bd-b7f7599fcaf0" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_019e40ee-b039-7526-9e09-696e3bc66c3e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_AdjustmentsToAdditionalPaidInCapitalSeparationTransactionAdjustments_019e40ee-b039-7b63-aa3e-61e351c45fc6" xlink:href="q-20260630.xsd#q_AdjustmentsToAdditionalPaidInCapitalSeparationTransactionAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e40ee-b039-7ed3-80bd-b7f7599fcaf0" xlink:to="loc_q_AdjustmentsToAdditionalPaidInCapitalSeparationTransactionAdjustments_019e40ee-b039-7b63-aa3e-61e351c45fc6" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityOther_019e40ee-b039-7b9b-ad9a-49baad40c8bc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e40ee-b039-7ed3-80bd-b7f7599fcaf0" xlink:to="loc_us-gaap_StockholdersEquityOther_019e40ee-b039-7b9b-ad9a-49baad40c8bc" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019e40ee-b039-797b-8e20-07e90e133299" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/REVENUENarrativeDetails" xlink:type="simple" xlink:href="q-20260630.xsd#REVENUENarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/REVENUENarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019e40ee-b039-7731-b20f-f5b8147839c0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019e40ee-b039-7e18-89cd-4f3bda5a8acf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019e40ee-b039-7731-b20f-f5b8147839c0" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019e40ee-b039-7e18-89cd-4f3bda5a8acf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019e40ee-b039-70f6-8aa0-79fdc8035976" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019e40ee-b039-7e18-89cd-4f3bda5a8acf" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019e40ee-b039-70f6-8aa0-79fdc8035976" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019e40ee-b039-70f6-8aa0-79fdc8035976_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019e40ee-b039-70f6-8aa0-79fdc8035976" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019e40ee-b039-70f6-8aa0-79fdc8035976_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019e40ee-b039-7726-8e1b-48df41e73f1a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019e40ee-b039-70f6-8aa0-79fdc8035976" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019e40ee-b039-7726-8e1b-48df41e73f1a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesRevenueNetMember_019e40ee-b039-71c4-bdb8-2dbbb9cb9aa9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SalesRevenueNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019e40ee-b039-7726-8e1b-48df41e73f1a" xlink:to="loc_us-gaap_SalesRevenueNetMember_019e40ee-b039-71c4-bdb8-2dbbb9cb9aa9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_019e40ee-b039-7cdf-8ad7-43251c25d357" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019e40ee-b039-7e18-89cd-4f3bda5a8acf" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_019e40ee-b039-7cdf-8ad7-43251c25d357" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_019e40ee-b039-7cdf-8ad7-43251c25d357_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_019e40ee-b039-7cdf-8ad7-43251c25d357" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_019e40ee-b039-7cdf-8ad7-43251c25d357_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_019e40ee-b039-7597-8791-f6eea0318597" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_019e40ee-b039-7cdf-8ad7-43251c25d357" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_019e40ee-b039-7597-8791-f6eea0318597" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_019e40ee-b039-7ee6-be58-b0b2e72a490b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_019e40ee-b039-7597-8791-f6eea0318597" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_019e40ee-b039-7ee6-be58-b0b2e72a490b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_019e40ee-b039-787d-88e1-d5c1e448009d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019e40ee-b039-7e18-89cd-4f3bda5a8acf" xlink:to="loc_srt_MajorCustomersAxis_019e40ee-b039-787d-88e1-d5c1e448009d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_019e40ee-b039-787d-88e1-d5c1e448009d_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_019e40ee-b039-787d-88e1-d5c1e448009d" xlink:to="loc_srt_NameOfMajorCustomerDomain_019e40ee-b039-787d-88e1-d5c1e448009d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_019e40ee-b039-79ab-91af-8168b70d548e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_019e40ee-b039-787d-88e1-d5c1e448009d" xlink:to="loc_srt_NameOfMajorCustomerDomain_019e40ee-b039-79ab-91af-8168b70d548e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SamsungElectronicsCompanyLimitedMember_019e40ee-b039-70eb-896c-a28db6ec3b20" xlink:href="q-20260630.xsd#q_SamsungElectronicsCompanyLimitedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_019e40ee-b039-79ab-91af-8168b70d548e" xlink:to="loc_q_SamsungElectronicsCompanyLimitedMember_019e40ee-b039-70eb-896c-a28db6ec3b20" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_TaiwanSemiconductorManufacturingCompanyLimitedMember_019e40ee-b039-7a66-b2c7-b83348248694" xlink:href="q-20260630.xsd#q_TaiwanSemiconductorManufacturingCompanyLimitedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_019e40ee-b039-79ab-91af-8168b70d548e" xlink:to="loc_q_TaiwanSemiconductorManufacturingCompanyLimitedMember_019e40ee-b039-7a66-b2c7-b83348248694" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_019e40ee-b039-702c-8333-a343cc234734" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019e40ee-b039-7731-b20f-f5b8147839c0" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_019e40ee-b039-702c-8333-a343cc234734" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/REVENUEScheduleofDisaggregationofRevenueDetails" xlink:type="simple" xlink:href="q-20260630.xsd#REVENUEScheduleofDisaggregationofRevenueDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/REVENUEScheduleofDisaggregationofRevenueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019e40ee-b039-7d6a-ad30-477224ea3cc5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019e40ee-b039-7e8f-ba8b-76b8464b9b39" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019e40ee-b039-7d6a-ad30-477224ea3cc5" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019e40ee-b039-7e8f-ba8b-76b8464b9b39" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b039-77ea-864d-4f20e43f4f41" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019e40ee-b039-7e8f-ba8b-76b8464b9b39" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b039-77ea-864d-4f20e43f4f41" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e40ee-b039-77ea-864d-4f20e43f4f41_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b039-77ea-864d-4f20e43f4f41" xlink:to="loc_us-gaap_SegmentDomain_019e40ee-b039-77ea-864d-4f20e43f4f41_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e40ee-b039-7acf-bd7d-89ea9cbd4c7c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b039-77ea-864d-4f20e43f4f41" xlink:to="loc_us-gaap_SegmentDomain_019e40ee-b039-7acf-bd7d-89ea9cbd4c7c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SemiconductorTechnologiesMember_019e40ee-b039-722a-a733-e5454f5dfcf3" xlink:href="q-20260630.xsd#q_SemiconductorTechnologiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e40ee-b039-7acf-bd7d-89ea9cbd4c7c" xlink:to="loc_q_SemiconductorTechnologiesMember_019e40ee-b039-722a-a733-e5454f5dfcf3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_InterconnectSolutionsMember_019e40ee-b039-75de-bbbe-7c8ea69025f5" xlink:href="q-20260630.xsd#q_InterconnectSolutionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e40ee-b039-7acf-bd7d-89ea9cbd4c7c" xlink:to="loc_q_InterconnectSolutionsMember_019e40ee-b039-75de-bbbe-7c8ea69025f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019e40ee-b039-7062-90c5-d19f97c34e37" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019e40ee-b039-7e8f-ba8b-76b8464b9b39" xlink:to="loc_srt_StatementGeographicalAxis_019e40ee-b039-7062-90c5-d19f97c34e37" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019e40ee-b039-7062-90c5-d19f97c34e37_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019e40ee-b039-7062-90c5-d19f97c34e37" xlink:to="loc_srt_SegmentGeographicalDomain_019e40ee-b039-7062-90c5-d19f97c34e37_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019e40ee-b039-73f1-91af-d820e1c6d9fc" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019e40ee-b039-7062-90c5-d19f97c34e37" xlink:to="loc_srt_SegmentGeographicalDomain_019e40ee-b039-73f1-91af-d820e1c6d9fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AmericasMember_019e40ee-b039-7d17-86dd-c6d3a2bc9688" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_AmericasMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019e40ee-b039-73f1-91af-d820e1c6d9fc" xlink:to="loc_srt_AmericasMember_019e40ee-b039-7d17-86dd-c6d3a2bc9688" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_019e40ee-b039-7006-9dcd-3f7d7f06ad69" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019e40ee-b039-73f1-91af-d820e1c6d9fc" xlink:to="loc_country_US_019e40ee-b039-7006-9dcd-3f7d7f06ad69" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_AmericasExcludingTheUnitedStatesMember_019e40ee-b039-7012-b9be-12388d4d3915" xlink:href="q-20260630.xsd#q_AmericasExcludingTheUnitedStatesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019e40ee-b039-73f1-91af-d820e1c6d9fc" xlink:to="loc_q_AmericasExcludingTheUnitedStatesMember_019e40ee-b039-7012-b9be-12388d4d3915" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EMEAMember_019e40ee-b039-7602-9de0-c70158688db5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EMEAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019e40ee-b039-73f1-91af-d820e1c6d9fc" xlink:to="loc_us-gaap_EMEAMember_019e40ee-b039-7602-9de0-c70158688db5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AsiaPacificMember_019e40ee-b039-7bd6-bb01-a080d76b71da" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_AsiaPacificMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019e40ee-b039-73f1-91af-d820e1c6d9fc" xlink:to="loc_srt_AsiaPacificMember_019e40ee-b039-7bd6-bb01-a080d76b71da" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CN_019e40ee-b039-7f2e-b4c7-1c595db80cf8" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_CN"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_AsiaPacificMember_019e40ee-b039-7bd6-bb01-a080d76b71da" xlink:to="loc_country_CN_019e40ee-b039-7f2e-b4c7-1c595db80cf8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SouthKoreaTaiwanAndOtherAsiaPacificMember_019e40ee-b039-7f8e-b1c6-9cfa372fd3d6" xlink:href="q-20260630.xsd#q_SouthKoreaTaiwanAndOtherAsiaPacificMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_AsiaPacificMember_019e40ee-b039-7bd6-bb01-a080d76b71da" xlink:to="loc_q_SouthKoreaTaiwanAndOtherAsiaPacificMember_019e40ee-b039-7f8e-b1c6-9cfa372fd3d6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_KR_019e40ee-b039-7b8f-b5c4-134f10701461" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_KR"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_q_SouthKoreaTaiwanAndOtherAsiaPacificMember_019e40ee-b039-7f8e-b1c6-9cfa372fd3d6" xlink:to="loc_country_KR_019e40ee-b039-7b8f-b5c4-134f10701461" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_TW_019e40ee-b039-7cbf-8d98-bec56568002b" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_TW"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_q_SouthKoreaTaiwanAndOtherAsiaPacificMember_019e40ee-b039-7f8e-b1c6-9cfa372fd3d6" xlink:to="loc_country_TW_019e40ee-b039-7cbf-8d98-bec56568002b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_OtherMember_019e40ee-b039-7eca-987f-f56275151351" xlink:href="q-20260630.xsd#q_OtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_q_SouthKoreaTaiwanAndOtherAsiaPacificMember_019e40ee-b039-7f8e-b1c6-9cfa372fd3d6" xlink:to="loc_q_OtherMember_019e40ee-b039-7eca-987f-f56275151351" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019e40ee-b039-7463-a510-67ba27cb9f7f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019e40ee-b039-7d6a-ad30-477224ea3cc5" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019e40ee-b039-7463-a510-67ba27cb9f7f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/TRANSFORMATIONINTEGRATIONANDOTHERCHARGESScheduleofTransformationIntegrationandOtherChargesbyCostCategoryDetails" xlink:type="simple" xlink:href="q-20260630.xsd#TRANSFORMATIONINTEGRATIONANDOTHERCHARGESScheduleofTransformationIntegrationandOtherChargesbyCostCategoryDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/TRANSFORMATIONINTEGRATIONANDOTHERCHARGESScheduleofTransformationIntegrationandOtherChargesbyCostCategoryDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_019fa94a-2cd3-733b-9f7f-8f525eee42bf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringCostAndReserveLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019fa94a-2cd3-7dce-8d93-6890da1e9f7f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_019fa94a-2cd3-733b-9f7f-8f525eee42bf" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019fa94a-2cd3-7dce-8d93-6890da1e9f7f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanAxis_019fa94a-2cd3-74c3-a760-5447a1b8050b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringPlanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_019fa94a-2cd3-7dce-8d93-6890da1e9f7f" xlink:to="loc_us-gaap_RestructuringPlanAxis_019fa94a-2cd3-74c3-a760-5447a1b8050b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanDomain_019fa94a-2cd3-74c3-a760-5447a1b8050b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringPlanAxis_019fa94a-2cd3-74c3-a760-5447a1b8050b" xlink:to="loc_us-gaap_RestructuringPlanDomain_019fa94a-2cd3-74c3-a760-5447a1b8050b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanDomain_019fa94a-2cd3-7a71-9406-ddd3ffdd22a9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestructuringPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringPlanAxis_019fa94a-2cd3-74c3-a760-5447a1b8050b" xlink:to="loc_us-gaap_RestructuringPlanDomain_019fa94a-2cd3-7a71-9406-ddd3ffdd22a9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_PreSeparationRestructuringProgramsMember_019fa94a-2cd3-7cee-b6d0-293c01cc54e6" xlink:href="q-20260630.xsd#q_PreSeparationRestructuringProgramsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringPlanDomain_019fa94a-2cd3-7a71-9406-ddd3ffdd22a9" xlink:to="loc_q_PreSeparationRestructuringProgramsMember_019fa94a-2cd3-7cee-b6d0-293c01cc54e6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_TransformationPlanMember_019fa94a-2cd3-7215-8376-c55c35a27bb8" xlink:href="q-20260630.xsd#q_TransformationPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringPlanDomain_019fa94a-2cd3-7a71-9406-ddd3ffdd22a9" xlink:to="loc_q_TransformationPlanMember_019fa94a-2cd3-7215-8376-c55c35a27bb8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeveranceCosts1_019e40ee-b125-7d2a-a307-d680bc0a2c53" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeveranceCosts1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_019fa94a-2cd3-733b-9f7f-8f525eee42bf" xlink:to="loc_us-gaap_SeveranceCosts1_019e40ee-b125-7d2a-a307-d680bc0a2c53" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_ITIndependence_019e40ee-b125-7516-a1e3-899f74461bcc" xlink:href="q-20260630.xsd#q_ITIndependence"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_019fa94a-2cd3-733b-9f7f-8f525eee42bf" xlink:to="loc_q_ITIndependence_019e40ee-b125-7516-a1e3-899f74461bcc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_TransformationInitiativeCharges_019e40ee-b125-7328-8d03-1312006cde02" xlink:href="q-20260630.xsd#q_TransformationInitiativeCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_019fa94a-2cd3-733b-9f7f-8f525eee42bf" xlink:to="loc_q_TransformationInitiativeCharges_019e40ee-b125-7328-8d03-1312006cde02" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_IntegrationAndOther_019e40ee-b125-74d7-821a-e0c49e26e7c9" xlink:href="q-20260630.xsd#q_IntegrationAndOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_019fa94a-2cd3-733b-9f7f-8f525eee42bf" xlink:to="loc_q_IntegrationAndOther_019e40ee-b125-74d7-821a-e0c49e26e7c9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeveranceCosts1_019eca12-1dd9-7871-8949-ed4ee57cc871" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeveranceCosts1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetImpairmentCharges_019f69e6-bde0-798c-b93a-e845e2364d04" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetImpairmentCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_019fa94a-2cd3-733b-9f7f-8f525eee42bf" xlink:to="loc_us-gaap_AssetImpairmentCharges_019f69e6-bde0-798c-b93a-e845e2364d04" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_TransformationIntegrationAndOtherCharges_019e40ee-b125-7ed0-9fb2-45dcb3e3a99f" xlink:href="q-20260630.xsd#q_TransformationIntegrationAndOtherCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_019fa94a-2cd3-733b-9f7f-8f525eee42bf" xlink:to="loc_q_TransformationIntegrationAndOtherCharges_019e40ee-b125-7ed0-9fb2-45dcb3e3a99f" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/RELATIONSHIPWITHDUPONTScheduleofCorporateExpenseAllocationsDetails" xlink:type="simple" xlink:href="q-20260630.xsd#RELATIONSHIPWITHDUPONTScheduleofCorporateExpenseAllocationsDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/RELATIONSHIPWITHDUPONTScheduleofCorporateExpenseAllocationsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019e40ee-b125-7f6b-a432-b32f7d5d5236" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e40ee-b125-7fde-9cd4-eb2283a0e588" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e40ee-b125-7f6b-a432-b32f7d5d5236" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e40ee-b125-7fde-9cd4-eb2283a0e588" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e40ee-b125-7743-9745-a98bf2374760" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e40ee-b125-7fde-9cd4-eb2283a0e588" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e40ee-b125-7743-9745-a98bf2374760" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e40ee-b125-7743-9745-a98bf2374760_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e40ee-b125-7743-9745-a98bf2374760" xlink:to="loc_us-gaap_RelatedPartyDomain_019e40ee-b125-7743-9745-a98bf2374760_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e40ee-b125-72e2-92f3-1e891532afde" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e40ee-b125-7743-9745-a98bf2374760" xlink:to="loc_us-gaap_RelatedPartyDomain_019e40ee-b125-72e2-92f3-1e891532afde" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019e40ee-b125-7afa-88b7-de4c9b9272dd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019e40ee-b125-72e2-92f3-1e891532afde" xlink:to="loc_us-gaap_RelatedPartyMember_019e40ee-b125-7afa-88b7-de4c9b9272dd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_019e40ee-b125-72bd-b58f-df7cbe973f9f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e40ee-b125-7f6b-a432-b32f7d5d5236" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_019e40ee-b125-72bd-b58f-df7cbe973f9f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_019e40ee-b125-7c7e-9740-c02e6048ba5f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e40ee-b125-7f6b-a432-b32f7d5d5236" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_019e40ee-b125-7c7e-9740-c02e6048ba5f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_019e40ee-b125-7567-bf91-35104ffb6e88" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e40ee-b125-7f6b-a432-b32f7d5d5236" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_019e40ee-b125-7567-bf91-35104ffb6e88" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_TransformationIntegrationAndOtherCharges_019e40ee-b125-777d-a725-29da51a21a9b" xlink:href="q-20260630.xsd#q_TransformationIntegrationAndOtherCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e40ee-b125-7f6b-a432-b32f7d5d5236" xlink:to="loc_q_TransformationIntegrationAndOtherCharges_019e40ee-b125-777d-a725-29da51a21a9b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_019e40ee-b125-72d0-bce0-1448caf8885c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e40ee-b125-7f6b-a432-b32f7d5d5236" xlink:to="loc_us-gaap_OperatingExpenses_019e40ee-b125-72d0-bce0-1448caf8885c" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/RELATIONSHIPWITHDUPONTScheduleofParentCompanyEquityDetails" xlink:type="simple" xlink:href="q-20260630.xsd#RELATIONSHIPWITHDUPONTScheduleofParentCompanyEquityDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/RELATIONSHIPWITHDUPONTScheduleofParentCompanyEquityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019e40ee-b125-7d69-a59c-23842dcd84a7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e40ee-b125-70e7-b640-4325912d982b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e40ee-b125-7d69-a59c-23842dcd84a7" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e40ee-b125-70e7-b640-4325912d982b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e40ee-b125-70ae-af67-dd3f5fc5cfab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e40ee-b125-70e7-b640-4325912d982b" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e40ee-b125-70ae-af67-dd3f5fc5cfab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e40ee-b125-70ae-af67-dd3f5fc5cfab_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e40ee-b125-70ae-af67-dd3f5fc5cfab" xlink:to="loc_us-gaap_RelatedPartyDomain_019e40ee-b125-70ae-af67-dd3f5fc5cfab_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e40ee-b125-7975-97ab-21ccc8a6115b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e40ee-b125-70ae-af67-dd3f5fc5cfab" xlink:to="loc_us-gaap_RelatedPartyDomain_019e40ee-b125-7975-97ab-21ccc8a6115b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019e40ee-b125-75d2-a02f-c6a81d175dbe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019e40ee-b125-7975-97ab-21ccc8a6115b" xlink:to="loc_us-gaap_RelatedPartyMember_019e40ee-b125-75d2-a02f-c6a81d175dbe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_CashPoolingAndGeneralFinancingActivities_019e40ee-b125-7a0d-b00c-90ed7865980d" xlink:href="q-20260630.xsd#q_CashPoolingAndGeneralFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e40ee-b125-7d69-a59c-23842dcd84a7" xlink:to="loc_q_CashPoolingAndGeneralFinancingActivities_019e40ee-b125-7a0d-b00c-90ed7865980d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_CorporateCostAllocations_019e40ee-b125-70a5-b98c-08ba65e17152" xlink:href="q-20260630.xsd#q_CorporateCostAllocations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e40ee-b125-7d69-a59c-23842dcd84a7" xlink:to="loc_q_CorporateCostAllocations_019e40ee-b125-70a5-b98c-08ba65e17152" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_TaxesDeemedSettledWithParent_019e40ee-b125-73ee-b807-1573807d1a84" xlink:href="q-20260630.xsd#q_TaxesDeemedSettledWithParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e40ee-b125-7d69-a59c-23842dcd84a7" xlink:to="loc_q_TaxesDeemedSettledWithParent_019e40ee-b125-73ee-b807-1573807d1a84" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_PaymentToTransfersToParentNet_019e40ee-b125-7f3a-a42d-c37b34c4ba4e" xlink:href="q-20260630.xsd#q_PaymentToTransfersToParentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e40ee-b125-7d69-a59c-23842dcd84a7" xlink:to="loc_q_PaymentToTransfersToParentNet_019e40ee-b125-7f3a-a42d-c37b34c4ba4e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_StockBasedCompensationAndOtherNoncashTransfersToParent_019e40ee-b125-754c-9e22-df954a88b70a" xlink:href="q-20260630.xsd#q_StockBasedCompensationAndOtherNoncashTransfersToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e40ee-b125-7d69-a59c-23842dcd84a7" xlink:to="loc_q_StockBasedCompensationAndOtherNoncashTransfersToParent_019e40ee-b125-754c-9e22-df954a88b70a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_ParentCompanyEquityTransfersToParentNet_019e40ee-b125-7ee0-ab32-c7712e83fd0b" xlink:href="q-20260630.xsd#q_ParentCompanyEquityTransfersToParentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e40ee-b125-7d69-a59c-23842dcd84a7" xlink:to="loc_q_ParentCompanyEquityTransfersToParentNet_019e40ee-b125-7ee0-ab32-c7712e83fd0b" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/NONCONSOLIDATEDAFFILIATESDetails" xlink:type="simple" xlink:href="q-20260630.xsd#NONCONSOLIDATEDAFFILIATESDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/NONCONSOLIDATEDAFFILIATESDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfInvestmentsLineItems_019e40ee-b125-77ee-9f68-9e8079605a7a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesTable_019e40ee-b125-73aa-b690-c7f637e66cd0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentsInAndAdvancesToAffiliatesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019e40ee-b125-77ee-9f68-9e8079605a7a" xlink:to="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesTable_019e40ee-b125-73aa-b690-c7f637e66cd0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_019e40ee-b125-7536-9337-e3dc7500f98f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesTable_019e40ee-b125-73aa-b690-c7f637e66cd0" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_019e40ee-b125-7536-9337-e3dc7500f98f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_019e40ee-b125-7536-9337-e3dc7500f98f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_019e40ee-b125-7536-9337-e3dc7500f98f" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_019e40ee-b125-7536-9337-e3dc7500f98f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_019e40ee-b125-71b5-bc92-6c80e981b15a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_019e40ee-b125-7536-9337-e3dc7500f98f" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_019e40ee-b125-71b5-bc92-6c80e981b15a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_HitachiChemDuPMicrosystemsLLCMember_019e40ee-b125-79ea-9209-f6669a3a3e1e" xlink:href="q-20260630.xsd#q_HitachiChemDuPMicrosystemsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_019e40ee-b125-71b5-bc92-6c80e981b15a" xlink:to="loc_q_HitachiChemDuPMicrosystemsLLCMember_019e40ee-b125-79ea-9209-f6669a3a3e1e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e40ee-b125-7045-b07c-ed272f3e2d30" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesTable_019e40ee-b125-73aa-b690-c7f637e66cd0" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e40ee-b125-7045-b07c-ed272f3e2d30" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e40ee-b125-7045-b07c-ed272f3e2d30_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e40ee-b125-7045-b07c-ed272f3e2d30" xlink:to="loc_us-gaap_RelatedPartyDomain_019e40ee-b125-7045-b07c-ed272f3e2d30_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e40ee-b125-7cb6-98fd-e3115a533117" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e40ee-b125-7045-b07c-ed272f3e2d30" xlink:to="loc_us-gaap_RelatedPartyDomain_019e40ee-b125-7cb6-98fd-e3115a533117" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019e40ee-b125-76e5-b763-c0d6e16bbf19" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019e40ee-b125-7cb6-98fd-e3115a533117" xlink:to="loc_us-gaap_RelatedPartyMember_019e40ee-b125-76e5-b763-c0d6e16bbf19" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvesteeMember_019e40ee-b125-7f09-ad14-d76f078ca287" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvesteeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019e40ee-b125-7cb6-98fd-e3115a533117" xlink:to="loc_us-gaap_EquityMethodInvesteeMember_019e40ee-b125-7f09-ad14-d76f078ca287" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019e40ee-b125-7a84-a071-e5e65d96921b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesTable_019e40ee-b125-73aa-b690-c7f637e66cd0" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019e40ee-b125-7a84-a071-e5e65d96921b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019e40ee-b125-7a84-a071-e5e65d96921b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019e40ee-b125-7a84-a071-e5e65d96921b" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019e40ee-b125-7a84-a071-e5e65d96921b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019e40ee-b125-7b7e-9593-a383cb0d6b2c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019e40ee-b125-7a84-a071-e5e65d96921b" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019e40ee-b125-7b7e-9593-a383cb0d6b2c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerMember_019e40ee-b125-7087-b4f7-cdbdee6562d7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019e40ee-b125-7b7e-9593-a383cb0d6b2c" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerMember_019e40ee-b125-7087-b4f7-cdbdee6562d7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsTotalMember_019e40ee-b125-711b-80c3-15a6c721e938" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostOfGoodsTotalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019e40ee-b125-7b7e-9593-a383cb0d6b2c" xlink:to="loc_us-gaap_CostOfGoodsTotalMember_019e40ee-b125-711b-80c3-15a6c721e938" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_019e40ee-b125-73cc-b500-43b951bba87f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_InvestmentsInAndAdvancesToAffiliatesTable_019e40ee-b125-73aa-b690-c7f637e66cd0" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_019e40ee-b125-73cc-b500-43b951bba87f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_019e40ee-b125-73cc-b500-43b951bba87f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_019e40ee-b125-73cc-b500-43b951bba87f" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_019e40ee-b125-73cc-b500-43b951bba87f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_019e40ee-b125-7ba7-800f-713e72873d3e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_019e40ee-b125-73cc-b500-43b951bba87f" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_019e40ee-b125-7ba7-800f-713e72873d3e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_019e40ee-b125-779f-bfa1-dfa51ccc6bc9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_019e40ee-b125-7ba7-800f-713e72873d3e" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_019e40ee-b125-779f-bfa1-dfa51ccc6bc9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SupplierConcentrationRiskMember_019e40ee-b125-7af2-a314-1c109c27b506" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SupplierConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_019e40ee-b125-7ba7-800f-713e72873d3e" xlink:to="loc_us-gaap_SupplierConcentrationRiskMember_019e40ee-b125-7af2-a314-1c109c27b506" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_EquityMethodInvestmentNetOfInvestmentLiabilities_019e40ee-b125-7248-8fda-4dd369b3d52c" xlink:href="q-20260630.xsd#q_EquityMethodInvestmentNetOfInvestmentLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019e40ee-b125-77ee-9f68-9e8079605a7a" xlink:to="loc_q_EquityMethodInvestmentNetOfInvestmentLiabilities_019e40ee-b125-7248-8fda-4dd369b3d52c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayable_019e40ee-b125-7b8f-a422-5dc69ff2517f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NotesPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019e40ee-b125-77ee-9f68-9e8079605a7a" xlink:to="loc_us-gaap_NotesPayable_019e40ee-b125-7b8f-a422-5dc69ff2517f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_019e40ee-b125-739c-917e-075f0269bc5b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019e40ee-b125-77ee-9f68-9e8079605a7a" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_019e40ee-b125-739c-917e-075f0269bc5b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_EquityMethodInvestmentOwnershipInterestNumberOfAffiliates_019e40ee-b125-7ef4-a549-1d0690fa5452" xlink:href="q-20260630.xsd#q_EquityMethodInvestmentOwnershipInterestNumberOfAffiliates"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfInvestmentsLineItems_019e40ee-b125-77ee-9f68-9e8079605a7a" xlink:to="loc_q_EquityMethodInvestmentOwnershipInterestNumberOfAffiliates_019e40ee-b125-7ef4-a549-1d0690fa5452" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/GOODWILLANDOTHERINTANGIBLEASSETSScheduleofGoodwillDetails" xlink:type="simple" xlink:href="q-20260630.xsd#GOODWILLANDOTHERINTANGIBLEASSETSScheduleofGoodwillDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/GOODWILLANDOTHERINTANGIBLEASSETSScheduleofGoodwillDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillLineItems_019e40ee-b125-716e-a40d-1be349927808" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GoodwillLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_019e40ee-b125-7d2e-b5c8-67af305444fa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfGoodwillTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_019e40ee-b125-716e-a40d-1be349927808" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_019e40ee-b125-7d2e-b5c8-67af305444fa" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b125-7f29-97fa-232d5cd51cce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_019e40ee-b125-7d2e-b5c8-67af305444fa" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b125-7f29-97fa-232d5cd51cce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e40ee-b125-7f29-97fa-232d5cd51cce_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b125-7f29-97fa-232d5cd51cce" xlink:to="loc_us-gaap_SegmentDomain_019e40ee-b125-7f29-97fa-232d5cd51cce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e40ee-b125-73f5-bf07-2150394442e0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b125-7f29-97fa-232d5cd51cce" xlink:to="loc_us-gaap_SegmentDomain_019e40ee-b125-73f5-bf07-2150394442e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SemiconductorTechnologiesMember_019e40ee-b125-70ea-b38d-c7cefa494b11" xlink:href="q-20260630.xsd#q_SemiconductorTechnologiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e40ee-b125-73f5-bf07-2150394442e0" xlink:to="loc_q_SemiconductorTechnologiesMember_019e40ee-b125-70ea-b38d-c7cefa494b11" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_InterconnectSolutionsMember_019e40ee-b125-799c-b264-f724f7195e9b" xlink:href="q-20260630.xsd#q_InterconnectSolutionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e40ee-b125-73f5-bf07-2150394442e0" xlink:to="loc_q_InterconnectSolutionsMember_019e40ee-b125-799c-b264-f724f7195e9b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillRollForward_019e40ee-b125-7ec8-9a80-e97aa878bd78" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GoodwillRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_019e40ee-b125-716e-a40d-1be349927808" xlink:to="loc_us-gaap_GoodwillRollForward_019e40ee-b125-7ec8-9a80-e97aa878bd78" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019e40ee-b125-7f89-aa91-d287745a6e69" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_019e40ee-b125-7ec8-9a80-e97aa878bd78" xlink:to="loc_us-gaap_Goodwill_019e40ee-b125-7f89-aa91-d287745a6e69" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillForeignCurrencyTranslationGainLoss_019e40ee-b125-7311-b874-cd1a6c9a927e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GoodwillForeignCurrencyTranslationGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_019e40ee-b125-7ec8-9a80-e97aa878bd78" xlink:to="loc_us-gaap_GoodwillForeignCurrencyTranslationGainLoss_019e40ee-b125-7311-b874-cd1a6c9a927e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019e40ee-b125-7f34-bf21-8556f0efe048" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Goodwill"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/GOODWILLANDOTHERINTANGIBLEASSETSScheduleofOtherIntangibleAssetsDetails" xlink:type="simple" xlink:href="q-20260630.xsd#GOODWILLANDOTHERINTANGIBLEASSETSScheduleofOtherIntangibleAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/GOODWILLANDOTHERINTANGIBLEASSETSScheduleofOtherIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019e40ee-b125-70a8-b588-16f410221383" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019e40ee-b125-783c-b2c7-d62e7d60a781" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019e40ee-b125-70a8-b588-16f410221383" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019e40ee-b125-783c-b2c7-d62e7d60a781" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019e40ee-b125-7f08-bac6-3b17d8f7613e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019e40ee-b125-783c-b2c7-d62e7d60a781" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019e40ee-b125-7f08-bac6-3b17d8f7613e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e40ee-b125-7f08-bac6-3b17d8f7613e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019e40ee-b125-7f08-bac6-3b17d8f7613e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e40ee-b125-7f08-bac6-3b17d8f7613e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e40ee-b125-78a7-be0b-73f4833ac70d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019e40ee-b125-7f08-bac6-3b17d8f7613e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e40ee-b125-78a7-be0b-73f4833ac70d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_019e40ee-b125-7c36-8da7-7002b01a8b86" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e40ee-b125-78a7-be0b-73f4833ac70d" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_019e40ee-b125-7c36-8da7-7002b01a8b86" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksAndTradeNamesMember_019e40ee-b125-766b-a5d2-130ad351332c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TrademarksAndTradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e40ee-b125-78a7-be0b-73f4833ac70d" xlink:to="loc_us-gaap_TrademarksAndTradeNamesMember_019e40ee-b125-766b-a5d2-130ad351332c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_019e40ee-b125-7ff3-bb68-4cca0c0fac00" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CustomerRelatedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e40ee-b125-78a7-be0b-73f4833ac70d" xlink:to="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_019e40ee-b125-7ff3-bb68-4cca0c0fac00" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_019e40ee-b125-737d-a18e-e3797611cd94" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019e40ee-b125-70a8-b588-16f410221383" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_019e40ee-b125-737d-a18e-e3797611cd94" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019e40ee-b125-77e5-bde7-ac857a9c8fa3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019e40ee-b125-70a8-b588-16f410221383" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019e40ee-b125-77e5-bde7-ac857a9c8fa3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019e40ee-b125-784a-bf4b-979219c4f8bc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019e40ee-b125-70a8-b588-16f410221383" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019e40ee-b125-784a-bf4b-979219c4f8bc" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/GOODWILLANDOTHERINTANGIBLEASSETSScheduleofIntangiblesbySegmentDetails" xlink:type="simple" xlink:href="q-20260630.xsd#GOODWILLANDOTHERINTANGIBLEASSETSScheduleofIntangiblesbySegmentDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/GOODWILLANDOTHERINTANGIBLEASSETSScheduleofIntangiblesbySegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_q_ScheduleofIntangibleAssetsLineItems_019e40ee-b125-72c0-9aa4-a10b51f5d60b" xlink:href="q-20260630.xsd#q_ScheduleofIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_ScheduleofIntangibleAssetsTable_019e40ee-b125-7d79-b1af-7a3059ea7b8b" xlink:href="q-20260630.xsd#q_ScheduleofIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_q_ScheduleofIntangibleAssetsLineItems_019e40ee-b125-72c0-9aa4-a10b51f5d60b" xlink:to="loc_q_ScheduleofIntangibleAssetsTable_019e40ee-b125-7d79-b1af-7a3059ea7b8b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019e40ee-b125-71ef-be91-57db1f5d1846" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_q_ScheduleofIntangibleAssetsTable_019e40ee-b125-7d79-b1af-7a3059ea7b8b" xlink:to="loc_srt_ConsolidationItemsAxis_019e40ee-b125-71ef-be91-57db1f5d1846" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019e40ee-b125-71ef-be91-57db1f5d1846_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019e40ee-b125-71ef-be91-57db1f5d1846" xlink:to="loc_srt_ConsolidationItemsDomain_019e40ee-b125-71ef-be91-57db1f5d1846_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019e40ee-b125-77da-a958-befa3a9a9cab" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019e40ee-b125-71ef-be91-57db1f5d1846" xlink:to="loc_srt_ConsolidationItemsDomain_019e40ee-b125-77da-a958-befa3a9a9cab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019e40ee-b125-784d-88fa-e3e92395f441" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019e40ee-b125-77da-a958-befa3a9a9cab" xlink:to="loc_us-gaap_OperatingSegmentsMember_019e40ee-b125-784d-88fa-e3e92395f441" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b125-720b-8108-ebe8f195df45" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_q_ScheduleofIntangibleAssetsTable_019e40ee-b125-7d79-b1af-7a3059ea7b8b" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b125-720b-8108-ebe8f195df45" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e40ee-b125-720b-8108-ebe8f195df45_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b125-720b-8108-ebe8f195df45" xlink:to="loc_us-gaap_SegmentDomain_019e40ee-b125-720b-8108-ebe8f195df45_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e40ee-b125-732b-a460-5f409ee2991a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b125-720b-8108-ebe8f195df45" xlink:to="loc_us-gaap_SegmentDomain_019e40ee-b125-732b-a460-5f409ee2991a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SemiconductorTechnologiesMember_019e40ee-b125-79df-8424-0b77da0bd25f" xlink:href="q-20260630.xsd#q_SemiconductorTechnologiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e40ee-b125-732b-a460-5f409ee2991a" xlink:to="loc_q_SemiconductorTechnologiesMember_019e40ee-b125-79df-8424-0b77da0bd25f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_IndustrialsCoSegmentMember_019e40ee-b125-73dc-858e-4624d091a0a9" xlink:href="q-20260630.xsd#q_IndustrialsCoSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e40ee-b125-732b-a460-5f409ee2991a" xlink:to="loc_q_IndustrialsCoSegmentMember_019e40ee-b125-73dc-858e-4624d091a0a9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019e40ee-b125-796f-85ab-17acf8708c86" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_q_ScheduleofIntangibleAssetsLineItems_019e40ee-b125-72c0-9aa4-a10b51f5d60b" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019e40ee-b125-796f-85ab-17acf8708c86" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/SHORTTERMBORROWINGSLONGTERMDEBTANDAVAILABLECREDITFACILITIESDetails" xlink:type="simple" xlink:href="q-20260630.xsd#SHORTTERMBORROWINGSLONGTERMDEBTANDAVAILABLECREDITFACILITIESDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/SHORTTERMBORROWINGSLONGTERMDEBTANDAVAILABLECREDITFACILITIESDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_019e40ee-b125-7791-a284-f76829587c02" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_019e40ee-b125-7c97-82a3-5662abcb4ff3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019e40ee-b125-7791-a284-f76829587c02" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_019e40ee-b125-7c97-82a3-5662abcb4ff3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019e40ee-b125-70a7-b8b7-8005237201b7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_019e40ee-b125-7c97-82a3-5662abcb4ff3" xlink:to="loc_us-gaap_DebtInstrumentAxis_019e40ee-b125-70a7-b8b7-8005237201b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e40ee-b125-70a7-b8b7-8005237201b7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e40ee-b125-70a7-b8b7-8005237201b7" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e40ee-b125-70a7-b8b7-8005237201b7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e40ee-b125-7a61-9c0c-25a3ec3680d3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e40ee-b125-70a7-b8b7-8005237201b7" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e40ee-b125-7a61-9c0c-25a3ec3680d3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SeniorSecuredCreditFacilitiesMember_019e40ee-b125-7028-bb41-28fede85c59f" xlink:href="q-20260630.xsd#q_SeniorSecuredCreditFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e40ee-b125-7a61-9c0c-25a3ec3680d3" xlink:to="loc_q_SeniorSecuredCreditFacilitiesMember_019e40ee-b125-7028-bb41-28fede85c59f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SeniorSecuredRevolvingFacilityMaturesOctober2030Member_019e40ee-b125-7c7d-83cc-fba67d3f0293" xlink:href="q-20260630.xsd#q_SeniorSecuredRevolvingFacilityMaturesOctober2030Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e40ee-b125-7a61-9c0c-25a3ec3680d3" xlink:to="loc_q_SeniorSecuredRevolvingFacilityMaturesOctober2030Member_019e40ee-b125-7c7d-83cc-fba67d3f0293" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019e40ee-b125-74f8-b71a-3f291ccc2224" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_019e40ee-b125-7c97-82a3-5662abcb4ff3" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019e40ee-b125-74f8-b71a-3f291ccc2224" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e40ee-b125-74f8-b71a-3f291ccc2224_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e40ee-b125-74f8-b71a-3f291ccc2224" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e40ee-b125-74f8-b71a-3f291ccc2224_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e40ee-b125-7e6b-b437-11a527c897da" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e40ee-b125-74f8-b71a-3f291ccc2224" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e40ee-b125-7e6b-b437-11a527c897da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_019e40ee-b125-7160-92f3-727d98c6eaa6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019e40ee-b125-7e6b-b437-11a527c897da" xlink:to="loc_us-gaap_LineOfCreditMember_019e40ee-b125-7160-92f3-727d98c6eaa6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_TermLoanFacilityMember_019eca85-7f6b-7916-9c5b-7e9092a67e60" xlink:href="q-20260630.xsd#q_TermLoanFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019e40ee-b125-7e6b-b437-11a527c897da" xlink:to="loc_q_TermLoanFacilityMember_019eca85-7f6b-7916-9c5b-7e9092a67e60" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_019e40ee-b125-7a53-ae9c-ef754162a73d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_019e40ee-b125-7c97-82a3-5662abcb4ff3" xlink:to="loc_us-gaap_CreditFacilityAxis_019e40ee-b125-7a53-ae9c-ef754162a73d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019e40ee-b125-7a53-ae9c-ef754162a73d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_019e40ee-b125-7a53-ae9c-ef754162a73d" xlink:to="loc_us-gaap_CreditFacilityDomain_019e40ee-b125-7a53-ae9c-ef754162a73d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019e40ee-b125-7b9a-ba71-53367409b396" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_019e40ee-b125-7a53-ae9c-ef754162a73d" xlink:to="loc_us-gaap_CreditFacilityDomain_019e40ee-b125-7b9a-ba71-53367409b396" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019e40ee-b125-7586-8046-b861994c32c0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019e40ee-b125-7b9a-ba71-53367409b396" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019e40ee-b125-7586-8046-b861994c32c0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_019e40ee-b125-71c4-95f2-e99855fcc875" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019e40ee-b125-7b9a-ba71-53367409b396" xlink:to="loc_us-gaap_LetterOfCreditMember_019e40ee-b125-71c4-95f2-e99855fcc875" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_019eca41-83c3-7d9c-970d-7e62bb59bdbf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019e40ee-b125-7b9a-ba71-53367409b396" xlink:to="loc_us-gaap_SecuredDebtMember_019eca41-83c3-7d9c-970d-7e62bb59bdbf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e40ee-b125-7e6b-9d92-010c6ab7a0cd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_019e40ee-b125-7c97-82a3-5662abcb4ff3" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e40ee-b125-7e6b-9d92-010c6ab7a0cd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e40ee-b125-7e6b-9d92-010c6ab7a0cd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e40ee-b125-7e6b-9d92-010c6ab7a0cd" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e40ee-b125-7e6b-9d92-010c6ab7a0cd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e40ee-b125-72ad-8504-6e75d7e8ee7b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e40ee-b125-7e6b-9d92-010c6ab7a0cd" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e40ee-b125-72ad-8504-6e75d7e8ee7b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019e40ee-b125-7ce1-8ac7-95b9f8e19e36" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e40ee-b125-72ad-8504-6e75d7e8ee7b" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019e40ee-b125-7ce1-8ac7-95b9f8e19e36" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019fccbf-fcc5-7366-9a6f-53052b4b4dc2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_019e40ee-b125-7c97-82a3-5662abcb4ff3" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019fccbf-fcc5-7366-9a6f-53052b4b4dc2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019fccbf-fcc5-7366-9a6f-53052b4b4dc2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019fccbf-fcc5-7366-9a6f-53052b4b4dc2" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019fccbf-fcc5-7366-9a6f-53052b4b4dc2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019fccbf-fcc5-73d0-9e34-a6bc6ee4472e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019fccbf-fcc5-7366-9a6f-53052b4b4dc2" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019fccbf-fcc5-73d0-9e34-a6bc6ee4472e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019fccbf-fcc5-78aa-bb0d-d94a8aa8f812" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_019fccbf-fcc5-73d0-9e34-a6bc6ee4472e" xlink:to="loc_us-gaap_SubsequentEventMember_019fccbf-fcc5-78aa-bb0d-d94a8aa8f812" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtCurrent_019e40ee-b125-713b-8972-dc9d689d0e90" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019e40ee-b125-7791-a284-f76829587c02" xlink:to="loc_us-gaap_DebtCurrent_019e40ee-b125-713b-8972-dc9d689d0e90" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_019e40ee-b125-722c-bd45-7825871e43b5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019e40ee-b125-7791-a284-f76829587c02" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_019e40ee-b125-722c-bd45-7825871e43b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtFairValue_019e40ee-b125-7538-90c0-7182bf1a032a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019e40ee-b125-7791-a284-f76829587c02" xlink:to="loc_us-gaap_LongTermDebtFairValue_019e40ee-b125-7538-90c0-7182bf1a032a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_019eca85-7f6b-71d3-806d-53b80d1733ce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019e40ee-b125-7791-a284-f76829587c02" xlink:to="loc_us-gaap_DebtInstrumentTerm_019eca85-7f6b-71d3-806d-53b80d1733ce" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019e40ee-b125-7652-8c27-d50a607756c3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019e40ee-b125-7791-a284-f76829587c02" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019e40ee-b125-7652-8c27-d50a607756c3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_019eca85-7f6b-737a-bc7f-2eacb86fffb7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019e40ee-b125-7791-a284-f76829587c02" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_019eca85-7f6b-737a-bc7f-2eacb86fffb7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019eca85-7f6b-7e3c-8ef7-89a5f0774277" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019e40ee-b125-7791-a284-f76829587c02" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019eca85-7f6b-7e3c-8ef7-89a5f0774277" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromLinesOfCredit_019e40ee-b125-7c2a-93f1-a3bb7bf0e09c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019e40ee-b125-7791-a284-f76829587c02" xlink:to="loc_us-gaap_ProceedsFromLinesOfCredit_019e40ee-b125-7c2a-93f1-a3bb7bf0e09c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_019e40ee-b125-76d2-8215-8aa8b0ff4e6b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LettersOfCreditOutstandingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019e40ee-b125-7791-a284-f76829587c02" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_019e40ee-b125-76d2-8215-8aa8b0ff4e6b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_LineOfCreditFacilityRemainingBorrowingCapacityUncommittedAmount_019e40ee-b125-7c38-a7c7-4e6008211150" xlink:href="q-20260630.xsd#q_LineOfCreditFacilityRemainingBorrowingCapacityUncommittedAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_019e40ee-b125-7791-a284-f76829587c02" xlink:to="loc_q_LineOfCreditFacilityRemainingBorrowingCapacityUncommittedAmount_019e40ee-b125-7c38-a7c7-4e6008211150" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/COMMITMENTSANDCONTINGENTLIABILITIESDetails" xlink:type="simple" xlink:href="q-20260630.xsd#COMMITMENTSANDCONTINGENTLIABILITIESDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/COMMITMENTSANDCONTINGENTLIABILITIESDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_019e40ee-b126-72e2-8f43-434b1af87b71" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:to="loc_us-gaap_LossContingenciesTable_019e40ee-b126-72e2-8f43-434b1af87b71" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOfFinancialPositionLocationBalanceAxis_019e40ee-b126-7dea-8537-7525ebf946b7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementOfFinancialPositionLocationBalanceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019e40ee-b126-72e2-8f43-434b1af87b71" xlink:to="loc_us-gaap_StatementOfFinancialPositionLocationBalanceAxis_019e40ee-b126-7dea-8537-7525ebf946b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019e40ee-b126-7557-b329-241dbaedf972" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019e40ee-b126-72e2-8f43-434b1af87b71" xlink:to="loc_dei_LegalEntityAxis_019e40ee-b126-7557-b329-241dbaedf972" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e40ee-b126-7557-b329-241dbaedf972_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019e40ee-b126-7557-b329-241dbaedf972" xlink:to="loc_dei_EntityDomain_019e40ee-b126-7557-b329-241dbaedf972_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e40ee-b126-7dac-a2d7-cab9e996e673" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019e40ee-b126-7557-b329-241dbaedf972" xlink:to="loc_dei_EntityDomain_019e40ee-b126-7dac-a2d7-cab9e996e673" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_DuPontMember_019e40ee-b126-78e7-988d-a5c33599792d" xlink:href="q-20260630.xsd#q_DuPontMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019e40ee-b126-7dac-a2d7-cab9e996e673" xlink:to="loc_q_DuPontMember_019e40ee-b126-78e7-988d-a5c33599792d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_019e40ee-b126-7168-bd5d-906acabd8466" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019e40ee-b126-72e2-8f43-434b1af87b71" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_019e40ee-b126-7168-bd5d-906acabd8466" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_019e40ee-b126-7168-bd5d-906acabd8466_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_019e40ee-b126-7168-bd5d-906acabd8466" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_019e40ee-b126-7168-bd5d-906acabd8466_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_019e40ee-b126-72f0-9c84-0cd18b423b2f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_019e40ee-b126-7168-bd5d-906acabd8466" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_019e40ee-b126-72f0-9c84-0cd18b423b2f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_ApplicableQnityPercentageMember_019e40ee-b126-769d-b9e5-db82edc3fc03" xlink:href="q-20260630.xsd#q_ApplicableQnityPercentageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_019e40ee-b126-72f0-9c84-0cd18b423b2f" xlink:to="loc_q_ApplicableQnityPercentageMember_019e40ee-b126-769d-b9e5-db82edc3fc03" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_019e40ee-b126-7a90-a118-51cdbfb765f5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019e40ee-b126-72e2-8f43-434b1af87b71" xlink:to="loc_srt_LitigationCaseAxis_019e40ee-b126-7a90-a118-51cdbfb765f5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_019e40ee-b126-7a90-a118-51cdbfb765f5_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_019e40ee-b126-7a90-a118-51cdbfb765f5" xlink:to="loc_srt_LitigationCaseTypeDomain_019e40ee-b126-7a90-a118-51cdbfb765f5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_019e40ee-b126-72e1-b8ee-5a0bb475cdc9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_019e40ee-b126-7a90-a118-51cdbfb765f5" xlink:to="loc_srt_LitigationCaseTypeDomain_019e40ee-b126-72e1-b8ee-5a0bb475cdc9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_ConsentOrderForTheStateOfNewJerseyMattersMember_019e40ee-b126-7cee-b04c-b128e43390be" xlink:href="q-20260630.xsd#q_ConsentOrderForTheStateOfNewJerseyMattersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_019e40ee-b126-72e1-b8ee-5a0bb475cdc9" xlink:to="loc_q_ConsentOrderForTheStateOfNewJerseyMattersMember_019e40ee-b126-7cee-b04c-b128e43390be" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_StateOfNorthCarolinaAndMunicipalitiesMember_019fc7a1-2424-731f-85cc-b226736cbbb4" xlink:href="q-20260630.xsd#q_StateOfNorthCarolinaAndMunicipalitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_019e40ee-b126-72e1-b8ee-5a0bb475cdc9" xlink:to="loc_q_StateOfNorthCarolinaAndMunicipalitiesMember_019fc7a1-2424-731f-85cc-b226736cbbb4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_IndemnificationLiabilities_019e40ee-b126-729d-93f5-6c352d92f2bd" xlink:href="q-20260630.xsd#q_IndemnificationLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:to="loc_q_IndemnificationLiabilities_019e40ee-b126-729d-93f5-6c352d92f2bd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_IndemnificationLiabilitiesPotentialMaximumExposure_019e40ee-b126-756e-83f2-163ea14f68ce" xlink:href="q-20260630.xsd#q_IndemnificationLiabilitiesPotentialMaximumExposure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:to="loc_q_IndemnificationLiabilitiesPotentialMaximumExposure_019e40ee-b126-756e-83f2-163ea14f68ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_QualifiedSpendEligiblePFASCostsLifeToDate_019e40ee-b126-7d3e-9fcd-806334b69b93" xlink:href="q-20260630.xsd#q_QualifiedSpendEligiblePFASCostsLifeToDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:to="loc_q_QualifiedSpendEligiblePFASCostsLifeToDate_019e40ee-b126-7d3e-9fcd-806334b69b93" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionRate_019e40ee-b126-734d-81ee-776a29d5df92" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:to="loc_us-gaap_RelatedPartyTransactionRate_019e40ee-b126-734d-81ee-776a29d5df92" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_019e40ee-b126-737e-8823-ef90f9cd2ed6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LitigationSettlementAmountAwardedToOtherParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:to="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_019e40ee-b126-737e-8823-ef90f9cd2ed6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_ProposedLitigationSettlementPayablePeriod_019e40ee-b126-7530-8081-6981dfe2f6ef" xlink:href="q-20260630.xsd#q_ProposedLitigationSettlementPayablePeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:to="loc_q_ProposedLitigationSettlementPayablePeriod_019e40ee-b126-7530-8081-6981dfe2f6ef" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationReserve_019e40ee-b126-7e77-8ddd-a89f62da5402" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LitigationReserve"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:to="loc_us-gaap_LitigationReserve_019e40ee-b126-7e77-8ddd-a89f62da5402" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationSettlementInterest_019e40ee-b126-776c-b569-01fecb329a0b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LitigationSettlementInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:to="loc_us-gaap_LitigationSettlementInterest_019e40ee-b126-776c-b569-01fecb329a0b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyAccrualAtCarryingValue_019e40ee-b126-7dbf-87a0-4be06f979bbb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingencyAccrualAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:to="loc_us-gaap_LossContingencyAccrualAtCarryingValue_019e40ee-b126-7dbf-87a0-4be06f979bbb" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccrualForEnvironmentalLossContingencies_019e40ee-b126-7e96-b6d4-4b095d8920fc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccrualForEnvironmentalLossContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:to="loc_us-gaap_AccrualForEnvironmentalLossContingencies_019e40ee-b126-7e96-b6d4-4b095d8920fc" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/COMMITMENTSANDCONTINGENTLIABILITIESDetails_1" xlink:type="simple" xlink:href="q-20260630.xsd#COMMITMENTSANDCONTINGENTLIABILITIESDetails_1"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/COMMITMENTSANDCONTINGENTLIABILITIESDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_019e40ee-b126-72e2-8f43-434b1af87b71" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:to="loc_us-gaap_LossContingenciesTable_019e40ee-b126-72e2-8f43-434b1af87b71" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019e40ee-b126-7557-b329-241dbaedf972" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019e40ee-b126-72e2-8f43-434b1af87b71" xlink:to="loc_dei_LegalEntityAxis_019e40ee-b126-7557-b329-241dbaedf972" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e40ee-b126-7557-b329-241dbaedf972_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019e40ee-b126-7557-b329-241dbaedf972" xlink:to="loc_dei_EntityDomain_019e40ee-b126-7557-b329-241dbaedf972_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e40ee-b126-7dac-a2d7-cab9e996e673" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019e40ee-b126-7557-b329-241dbaedf972" xlink:to="loc_dei_EntityDomain_019e40ee-b126-7dac-a2d7-cab9e996e673" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_DuPontMember_019e40ee-b126-78e7-988d-a5c33599792d" xlink:href="q-20260630.xsd#q_DuPontMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019e40ee-b126-7dac-a2d7-cab9e996e673" xlink:to="loc_q_DuPontMember_019e40ee-b126-78e7-988d-a5c33599792d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_019e40ee-b126-7168-bd5d-906acabd8466" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019e40ee-b126-72e2-8f43-434b1af87b71" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_019e40ee-b126-7168-bd5d-906acabd8466" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_019e40ee-b126-7168-bd5d-906acabd8466_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_019e40ee-b126-7168-bd5d-906acabd8466" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_019e40ee-b126-7168-bd5d-906acabd8466_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_019e40ee-b126-72f0-9c84-0cd18b423b2f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_019e40ee-b126-7168-bd5d-906acabd8466" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_019e40ee-b126-72f0-9c84-0cd18b423b2f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_ApplicableQnityPercentageMember_019e40ee-b126-769d-b9e5-db82edc3fc03" xlink:href="q-20260630.xsd#q_ApplicableQnityPercentageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_019e40ee-b126-72f0-9c84-0cd18b423b2f" xlink:to="loc_q_ApplicableQnityPercentageMember_019e40ee-b126-769d-b9e5-db82edc3fc03" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_019e40ee-b126-7a90-a118-51cdbfb765f5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019e40ee-b126-72e2-8f43-434b1af87b71" xlink:to="loc_srt_LitigationCaseAxis_019e40ee-b126-7a90-a118-51cdbfb765f5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_019e40ee-b126-7a90-a118-51cdbfb765f5_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_019e40ee-b126-7a90-a118-51cdbfb765f5" xlink:to="loc_srt_LitigationCaseTypeDomain_019e40ee-b126-7a90-a118-51cdbfb765f5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_019e40ee-b126-72e1-b8ee-5a0bb475cdc9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_019e40ee-b126-7a90-a118-51cdbfb765f5" xlink:to="loc_srt_LitigationCaseTypeDomain_019e40ee-b126-72e1-b8ee-5a0bb475cdc9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_ConsentOrderForTheStateOfNewJerseyMattersMember_019e40ee-b126-7cee-b04c-b128e43390be" xlink:href="q-20260630.xsd#q_ConsentOrderForTheStateOfNewJerseyMattersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_019e40ee-b126-72e1-b8ee-5a0bb475cdc9" xlink:to="loc_q_ConsentOrderForTheStateOfNewJerseyMattersMember_019e40ee-b126-7cee-b04c-b128e43390be" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_StateOfNorthCarolinaAndMunicipalitiesMember_019fc7a1-2424-731f-85cc-b226736cbbb4" xlink:href="q-20260630.xsd#q_StateOfNorthCarolinaAndMunicipalitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_019e40ee-b126-72e1-b8ee-5a0bb475cdc9" xlink:to="loc_q_StateOfNorthCarolinaAndMunicipalitiesMember_019fc7a1-2424-731f-85cc-b226736cbbb4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_IndemnificationLiabilities_019e40ee-b126-729d-93f5-6c352d92f2bd" xlink:href="q-20260630.xsd#q_IndemnificationLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:to="loc_q_IndemnificationLiabilities_019e40ee-b126-729d-93f5-6c352d92f2bd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_IndemnificationLiabilitiesPotentialMaximumExposure_019e40ee-b126-756e-83f2-163ea14f68ce" xlink:href="q-20260630.xsd#q_IndemnificationLiabilitiesPotentialMaximumExposure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:to="loc_q_IndemnificationLiabilitiesPotentialMaximumExposure_019e40ee-b126-756e-83f2-163ea14f68ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_QualifiedSpendEligiblePFASCostsLifeToDate_019e40ee-b126-7d3e-9fcd-806334b69b93" xlink:href="q-20260630.xsd#q_QualifiedSpendEligiblePFASCostsLifeToDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:to="loc_q_QualifiedSpendEligiblePFASCostsLifeToDate_019e40ee-b126-7d3e-9fcd-806334b69b93" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionRate_019e40ee-b126-734d-81ee-776a29d5df92" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:to="loc_us-gaap_RelatedPartyTransactionRate_019e40ee-b126-734d-81ee-776a29d5df92" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_019e40ee-b126-737e-8823-ef90f9cd2ed6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LitigationSettlementAmountAwardedToOtherParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:to="loc_us-gaap_LitigationSettlementAmountAwardedToOtherParty_019e40ee-b126-737e-8823-ef90f9cd2ed6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_ProposedLitigationSettlementPayablePeriod_019e40ee-b126-7530-8081-6981dfe2f6ef" xlink:href="q-20260630.xsd#q_ProposedLitigationSettlementPayablePeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:to="loc_q_ProposedLitigationSettlementPayablePeriod_019e40ee-b126-7530-8081-6981dfe2f6ef" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationReserve_019e40ee-b126-7e77-8ddd-a89f62da5402" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LitigationReserve"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:to="loc_us-gaap_LitigationReserve_019e40ee-b126-7e77-8ddd-a89f62da5402" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LitigationSettlementInterest_019e40ee-b126-776c-b569-01fecb329a0b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LitigationSettlementInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:to="loc_us-gaap_LitigationSettlementInterest_019e40ee-b126-776c-b569-01fecb329a0b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyAccrualAtCarryingValue_019e40ee-b126-7dbf-87a0-4be06f979bbb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingencyAccrualAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:to="loc_us-gaap_LossContingencyAccrualAtCarryingValue_019e40ee-b126-7dbf-87a0-4be06f979bbb" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccrualForEnvironmentalLossContingencies_019e40ee-b126-7e96-b6d4-4b095d8920fc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccrualForEnvironmentalLossContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e40ee-b126-7e17-a497-2b91471cad59" xlink:to="loc_us-gaap_AccrualForEnvironmentalLossContingencies_019e40ee-b126-7e96-b6d4-4b095d8920fc" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/STOCKHOLDERSEQUITYNarrativeDetails" xlink:type="simple" xlink:href="q-20260630.xsd#STOCKHOLDERSEQUITYNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/STOCKHOLDERSEQUITYNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019e40ee-b126-7244-8037-d848bee3c2b9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019e40ee-b126-71f9-8198-7655dac351b8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019e40ee-b126-7244-8037-d848bee3c2b9" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019e40ee-b126-71f9-8198-7655dac351b8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramAxis_019e40ee-b126-7225-b0f7-e371921ef909" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ShareRepurchaseProgramAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019e40ee-b126-71f9-8198-7655dac351b8" xlink:to="loc_srt_ShareRepurchaseProgramAxis_019e40ee-b126-7225-b0f7-e371921ef909" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramDomain_019e40ee-b126-7225-b0f7-e371921ef909_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ShareRepurchaseProgramDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ShareRepurchaseProgramAxis_019e40ee-b126-7225-b0f7-e371921ef909" xlink:to="loc_srt_ShareRepurchaseProgramDomain_019e40ee-b126-7225-b0f7-e371921ef909_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramDomain_019e40ee-b126-7a87-9d87-d710e6d8a0c6" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ShareRepurchaseProgramDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ShareRepurchaseProgramAxis_019e40ee-b126-7225-b0f7-e371921ef909" xlink:to="loc_srt_ShareRepurchaseProgramDomain_019e40ee-b126-7a87-9d87-d710e6d8a0c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_A500MShareAuthorizationMember_019e40ee-b126-7a5e-9ac4-0dff61b68d74" xlink:href="q-20260630.xsd#q_A500MShareAuthorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ShareRepurchaseProgramDomain_019e40ee-b126-7a87-9d87-d710e6d8a0c6" xlink:to="loc_q_A500MShareAuthorizationMember_019e40ee-b126-7a5e-9ac4-0dff61b68d74" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StockRepurchaseProgramAuthorizedAmount1_019e40ee-b126-739d-9fa3-a495a4497393" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019e40ee-b126-7244-8037-d848bee3c2b9" xlink:to="loc_srt_StockRepurchaseProgramAuthorizedAmount1_019e40ee-b126-739d-9fa3-a495a4497393" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_019e40ee-b126-7869-a178-b5b1a79a3002" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019e40ee-b126-7244-8037-d848bee3c2b9" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_019e40ee-b126-7869-a178-b5b1a79a3002" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_019e40ee-b126-7a15-95a6-c9b2b05d33aa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019e40ee-b126-7244-8037-d848bee3c2b9" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_019e40ee-b126-7a15-95a6-c9b2b05d33aa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_019e40ee-b126-75c6-a5af-91ebd9a96236" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockAcquiredAverageCostPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019e40ee-b126-7244-8037-d848bee3c2b9" xlink:to="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_019e40ee-b126-75c6-a5af-91ebd9a96236" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_019e40ee-b126-73af-a615-2341e15f764c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019e40ee-b126-7244-8037-d848bee3c2b9" xlink:to="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_019e40ee-b126-73af-a615-2341e15f764c" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/STOCKHOLDERSEQUITYScheduleofAccumulatedOtherComprehensiveLossDetails" xlink:type="simple" xlink:href="q-20260630.xsd#STOCKHOLDERSEQUITYScheduleofAccumulatedOtherComprehensiveLossDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/STOCKHOLDERSEQUITYScheduleofAccumulatedOtherComprehensiveLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019e40ee-b126-7c44-8419-93a8b8c94c17" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019e40ee-b126-7ac4-bfe5-240ef2a069f7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019e40ee-b126-7c44-8419-93a8b8c94c17" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019e40ee-b126-7ac4-bfe5-240ef2a069f7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019e40ee-b126-7bdd-b695-0fad2247f5c3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_019e40ee-b126-7ac4-bfe5-240ef2a069f7" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019e40ee-b126-7bdd-b695-0fad2247f5c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019e40ee-b126-7bdd-b695-0fad2247f5c3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019e40ee-b126-7bdd-b695-0fad2247f5c3" xlink:to="loc_us-gaap_EquityComponentDomain_019e40ee-b126-7bdd-b695-0fad2247f5c3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019e40ee-b126-7d0a-bdc2-f3f57fe83265" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019e40ee-b126-7bdd-b695-0fad2247f5c3" xlink:to="loc_us-gaap_EquityComponentDomain_019e40ee-b126-7d0a-bdc2-f3f57fe83265" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019e40ee-b126-7c0c-9864-d6569933d7cb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e40ee-b126-7d0a-bdc2-f3f57fe83265" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019e40ee-b126-7c0c-9864-d6569933d7cb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_019e40ee-b126-76a6-9e50-8e2f6574226f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019e40ee-b126-7c0c-9864-d6569933d7cb" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_019e40ee-b126-76a6-9e50-8e2f6574226f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_019e40ee-b126-78c7-bf2a-8126ce0d12ff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019e40ee-b126-7c0c-9864-d6569933d7cb" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_019e40ee-b126-78c7-bf2a-8126ce0d12ff" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_019e40ee-b126-7093-a23e-22ea64efa323" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_019e40ee-b126-7c44-8419-93a8b8c94c17" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_019e40ee-b126-7093-a23e-22ea64efa323" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019e40ee-b126-745d-a9ef-54a6fd1febf5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_019e40ee-b126-7093-a23e-22ea64efa323" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019e40ee-b126-745d-a9ef-54a6fd1febf5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019e40ee-b126-7db9-aa7d-4a99c4e2ce9c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_019e40ee-b126-7093-a23e-22ea64efa323" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019e40ee-b126-7db9-aa7d-4a99c4e2ce9c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019e40ee-b126-745b-ad45-03ee8f66e325" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/STOCKBASEDCOMPENSATIONDetails" xlink:type="simple" xlink:href="q-20260630.xsd#STOCKBASEDCOMPENSATIONDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/STOCKBASEDCOMPENSATIONDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsLineItems_019e40ee-b126-7fd4-9ff1-22f4d08a6dc1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDeferredCompensationArrangementWithIndividualShareBasedPaymentsTable_019e40ee-b126-7a8d-9d7d-dc42a9644fb0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfDeferredCompensationArrangementWithIndividualShareBasedPaymentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsLineItems_019e40ee-b126-7fd4-9ff1-22f4d08a6dc1" xlink:to="loc_us-gaap_ScheduleOfDeferredCompensationArrangementWithIndividualShareBasedPaymentsTable_019e40ee-b126-7a8d-9d7d-dc42a9644fb0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_019e40ee-b126-76bc-9c0c-1980f82b38f6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDeferredCompensationArrangementWithIndividualShareBasedPaymentsTable_019e40ee-b126-7a8d-9d7d-dc42a9644fb0" xlink:to="loc_us-gaap_PlanNameAxis_019e40ee-b126-76bc-9c0c-1980f82b38f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_019e40ee-b126-76bc-9c0c-1980f82b38f6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_019e40ee-b126-76bc-9c0c-1980f82b38f6" xlink:to="loc_us-gaap_PlanNameDomain_019e40ee-b126-76bc-9c0c-1980f82b38f6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_019e40ee-b126-72a0-9d02-7f982ab6436f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_019e40ee-b126-76bc-9c0c-1980f82b38f6" xlink:to="loc_us-gaap_PlanNameDomain_019e40ee-b126-72a0-9d02-7f982ab6436f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_QnityElectronicsInc.EquityAndIncentivePlanMember_019e40ee-b126-7ad8-8faa-26ef855d9c91" xlink:href="q-20260630.xsd#q_QnityElectronicsInc.EquityAndIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_019e40ee-b126-72a0-9d02-7f982ab6436f" xlink:to="loc_q_QnityElectronicsInc.EquityAndIncentivePlanMember_019e40ee-b126-7ad8-8faa-26ef855d9c91" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019e40ee-b126-7a4b-b21a-4a81c0c25991" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDeferredCompensationArrangementWithIndividualShareBasedPaymentsTable_019e40ee-b126-7a8d-9d7d-dc42a9644fb0" xlink:to="loc_us-gaap_AwardTypeAxis_019e40ee-b126-7a4b-b21a-4a81c0c25991" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e40ee-b126-7a4b-b21a-4a81c0c25991_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019e40ee-b126-7a4b-b21a-4a81c0c25991" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e40ee-b126-7a4b-b21a-4a81c0c25991_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e40ee-b126-72e8-a8fd-4805491f6918" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019e40ee-b126-7a4b-b21a-4a81c0c25991" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e40ee-b126-72e8-a8fd-4805491f6918" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_019e40ee-b126-7a14-afe9-4c90dadf7c89" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e40ee-b126-72e8-a8fd-4805491f6918" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_019e40ee-b126-7a14-afe9-4c90dadf7c89" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_019e40ee-b126-70c9-a079-a261ae56483c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e40ee-b126-72e8-a8fd-4805491f6918" xlink:to="loc_us-gaap_PerformanceSharesMember_019e40ee-b126-70c9-a079-a261ae56483c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_019e40ee-b126-7315-a5c7-ac02668329ce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsLineItems_019e40ee-b126-7fd4-9ff1-22f4d08a6dc1" xlink:to="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_019e40ee-b126-7315-a5c7-ac02668329ce" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_019e40ee-b126-7fe3-af08-f41bbac58e82" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsLineItems_019e40ee-b126-7fd4-9ff1-22f4d08a6dc1" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_019e40ee-b126-7fe3-af08-f41bbac58e82" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense_019e40ee-b126-7763-90a9-8dba5238cd4d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsLineItems_019e40ee-b126-7fd4-9ff1-22f4d08a6dc1" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense_019e40ee-b126-7763-90a9-8dba5238cd4d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019e40ee-b126-7a07-9653-944b0b9a1d47" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsLineItems_019e40ee-b126-7fd4-9ff1-22f4d08a6dc1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019e40ee-b126-7a07-9653-944b0b9a1d47" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019e40ee-b126-7cc9-95f7-4e1a75a39c52" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsLineItems_019e40ee-b126-7fd4-9ff1-22f4d08a6dc1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019e40ee-b126-7cc9-95f7-4e1a75a39c52" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/FINANCIALINSTRUMENTSScheduleofFairValueofFinancialInstrumentsDetails" xlink:type="simple" xlink:href="q-20260630.xsd#FINANCIALINSTRUMENTSScheduleofFairValueofFinancialInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/FINANCIALINSTRUMENTSScheduleofFairValueofFinancialInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019e40ee-b126-74d0-826e-e9186ff17847" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019e40ee-b126-78d5-a5ec-0c07f686cdd4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019e40ee-b126-74d0-826e-e9186ff17847" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019e40ee-b126-78d5-a5ec-0c07f686cdd4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019e40ee-b126-7825-9f92-69a4c2f81279" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_019e40ee-b126-78d5-a5ec-0c07f686cdd4" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019e40ee-b126-7825-9f92-69a4c2f81279" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019e40ee-b126-7825-9f92-69a4c2f81279_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019e40ee-b126-7825-9f92-69a4c2f81279" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019e40ee-b126-7825-9f92-69a4c2f81279_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019e40ee-b126-7b73-b3b0-cd41f101cc0d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019e40ee-b126-7825-9f92-69a4c2f81279" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019e40ee-b126-7b73-b3b0-cd41f101cc0d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_019e40ee-b126-753a-b728-8635bd334e4d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019e40ee-b126-7b73-b3b0-cd41f101cc0d" xlink:to="loc_us-gaap_ForeignExchangeContractMember_019e40ee-b126-753a-b728-8635bd334e4d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashEquivalentsAtCarryingValue_019e40ee-b126-7202-913d-952f6576fe1d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019e40ee-b126-74d0-826e-e9186ff17847" xlink:to="loc_us-gaap_CashEquivalentsAtCarryingValue_019e40ee-b126-7202-913d-952f6576fe1d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsAbstract_019e40ee-b126-74d4-aec1-9b53708915b8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeAssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_019e40ee-b126-74d0-826e-e9186ff17847" xlink:to="loc_us-gaap_DerivativeAssetsAbstract_019e40ee-b126-74d4-aec1-9b53708915b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssets_019e40ee-b126-713d-abcd-d45652e704a8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeAssetsAbstract_019e40ee-b126-74d4-aec1-9b53708915b8" xlink:to="loc_us-gaap_DerivativeAssets_019e40ee-b126-713d-abcd-d45652e704a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_DerivativeAssetsLiabilitiesAccumulatedGrossUnrealizedGainBeforeTax_019e40ee-b126-71f2-8f56-7489a21a2301" xlink:href="q-20260630.xsd#q_DerivativeAssetsLiabilitiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeAssetsAbstract_019e40ee-b126-74d4-aec1-9b53708915b8" xlink:to="loc_q_DerivativeAssetsLiabilitiesAccumulatedGrossUnrealizedGainBeforeTax_019e40ee-b126-71f2-8f56-7489a21a2301" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_DerivativeAssetsLiabilitiesAccumulatedGrossUnrealizedLossBeforeTax_019e40ee-b126-7d19-94e5-14fc46021cea" xlink:href="q-20260630.xsd#q_DerivativeAssetsLiabilitiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeAssetsAbstract_019e40ee-b126-74d4-aec1-9b53708915b8" xlink:to="loc_q_DerivativeAssetsLiabilitiesAccumulatedGrossUnrealizedLossBeforeTax_019e40ee-b126-7d19-94e5-14fc46021cea" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet_019e40ee-b126-7438-a3bf-4af3a52f622c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeAssetsAbstract_019e40ee-b126-74d4-aec1-9b53708915b8" xlink:to="loc_us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet_019e40ee-b126-7438-a3bf-4af3a52f622c" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/FINANCIALINSTRUMENTSScheduleofNotionalAmountsDetails" xlink:type="simple" xlink:href="q-20260630.xsd#FINANCIALINSTRUMENTSScheduleofNotionalAmountsDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/FINANCIALINSTRUMENTSScheduleofNotionalAmountsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_019e40ee-b126-7e24-81a4-3703009a0582" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_019e40ee-b126-7782-a280-7518a1b319c1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_019e40ee-b126-7e24-81a4-3703009a0582" xlink:to="loc_us-gaap_DerivativeTable_019e40ee-b126-7782-a280-7518a1b319c1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019e40ee-b126-7d1d-ad93-070534b6a3d7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019e40ee-b126-7782-a280-7518a1b319c1" xlink:to="loc_us-gaap_HedgingDesignationAxis_019e40ee-b126-7d1d-ad93-070534b6a3d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019e40ee-b126-7d1d-ad93-070534b6a3d7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019e40ee-b126-7d1d-ad93-070534b6a3d7" xlink:to="loc_us-gaap_HedgingDesignationDomain_019e40ee-b126-7d1d-ad93-070534b6a3d7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019e40ee-b126-7aa1-9aba-6e1a39804147" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019e40ee-b126-7d1d-ad93-070534b6a3d7" xlink:to="loc_us-gaap_HedgingDesignationDomain_019e40ee-b126-7aa1-9aba-6e1a39804147" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_019e40ee-b126-7ccd-af9e-77f52ccdb1d4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019e40ee-b126-7aa1-9aba-6e1a39804147" xlink:to="loc_us-gaap_NondesignatedMember_019e40ee-b126-7ccd-af9e-77f52ccdb1d4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019e40ee-b126-7945-9187-d82d0f3894a8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019e40ee-b126-7782-a280-7518a1b319c1" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019e40ee-b126-7945-9187-d82d0f3894a8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019e40ee-b126-7945-9187-d82d0f3894a8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019e40ee-b126-7945-9187-d82d0f3894a8" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019e40ee-b126-7945-9187-d82d0f3894a8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019e40ee-b126-72d2-8bc7-1c3dbd7df1f5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019e40ee-b126-7945-9187-d82d0f3894a8" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019e40ee-b126-72d2-8bc7-1c3dbd7df1f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_019e40ee-b126-72a3-9df7-49d86c7e8683" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019e40ee-b126-72d2-8bc7-1c3dbd7df1f5" xlink:to="loc_us-gaap_ForeignExchangeContractMember_019e40ee-b126-72a3-9df7-49d86c7e8683" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_DerivativeNotionalAmountNet_019e40ee-b126-72c5-8641-e8fc74d708ec" xlink:href="q-20260630.xsd#q_DerivativeNotionalAmountNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019e40ee-b126-7e24-81a4-3703009a0582" xlink:to="loc_q_DerivativeNotionalAmountNet_019e40ee-b126-72c5-8641-e8fc74d708ec" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/FINANCIALINSTRUMENTSNarrativeDetails" xlink:type="simple" xlink:href="q-20260630.xsd#FINANCIALINSTRUMENTSNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/FINANCIALINSTRUMENTSNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_019e40ee-b126-7026-95b2-f1fe426f06c5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativesFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019e40ee-b126-791d-bbe0-5d8021e9e49c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019e40ee-b126-7026-95b2-f1fe426f06c5" xlink:to="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019e40ee-b126-791d-bbe0-5d8021e9e49c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019e40ee-b126-7eb8-a480-0a5053889b72" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019e40ee-b126-791d-bbe0-5d8021e9e49c" xlink:to="loc_us-gaap_HedgingDesignationAxis_019e40ee-b126-7eb8-a480-0a5053889b72" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019e40ee-b126-7eb8-a480-0a5053889b72_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019e40ee-b126-7eb8-a480-0a5053889b72" xlink:to="loc_us-gaap_HedgingDesignationDomain_019e40ee-b126-7eb8-a480-0a5053889b72_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019e40ee-b126-73e3-9a11-7120b34b61ad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019e40ee-b126-7eb8-a480-0a5053889b72" xlink:to="loc_us-gaap_HedgingDesignationDomain_019e40ee-b126-73e3-9a11-7120b34b61ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_019e40ee-b126-701d-8a03-7c02b578ff95" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019e40ee-b126-73e3-9a11-7120b34b61ad" xlink:to="loc_us-gaap_NondesignatedMember_019e40ee-b126-701d-8a03-7c02b578ff95" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019e40ee-b126-7b50-b41f-b44715b9100c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019e40ee-b126-791d-bbe0-5d8021e9e49c" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019e40ee-b126-7b50-b41f-b44715b9100c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019e40ee-b126-7b50-b41f-b44715b9100c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019e40ee-b126-7b50-b41f-b44715b9100c" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019e40ee-b126-7b50-b41f-b44715b9100c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019e40ee-b126-7870-8966-2dfaec2ca8c0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019e40ee-b126-7b50-b41f-b44715b9100c" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019e40ee-b126-7870-8966-2dfaec2ca8c0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_019e40ee-b126-7934-b6fe-bc468dab7fd1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019e40ee-b126-7870-8966-2dfaec2ca8c0" xlink:to="loc_us-gaap_ForeignExchangeContractMember_019e40ee-b126-7934-b6fe-bc468dab7fd1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet_019e40ee-b126-7c81-954b-b3a8654cef0b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019e40ee-b126-7026-95b2-f1fe426f06c5" xlink:to="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet_019e40ee-b126-7c81-954b-b3a8654cef0b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/FAIRVALUEMEASUREMENTSDetails" xlink:type="simple" xlink:href="q-20260630.xsd#FAIRVALUEMEASUREMENTSDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/FAIRVALUEMEASUREMENTSDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e40ee-b126-7926-83c9-46ee49411674" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e40ee-b126-7d1a-9a53-472b6a434bfd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e40ee-b126-7926-83c9-46ee49411674" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e40ee-b126-7d1a-9a53-472b6a434bfd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e40ee-b126-78a0-8241-ed99f37d48c9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e40ee-b126-7d1a-9a53-472b6a434bfd" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e40ee-b126-78a0-8241-ed99f37d48c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e40ee-b126-78a0-8241-ed99f37d48c9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e40ee-b126-78a0-8241-ed99f37d48c9" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e40ee-b126-78a0-8241-ed99f37d48c9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e40ee-b126-72cd-9866-f40dad903838" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e40ee-b126-78a0-8241-ed99f37d48c9" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e40ee-b126-72cd-9866-f40dad903838" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019e40ee-b126-77e4-ad17-7799dfd9cdf9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e40ee-b126-72cd-9866-f40dad903838" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019e40ee-b126-77e4-ad17-7799dfd9cdf9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019e40ee-b126-71cc-b347-7550399a24ff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e40ee-b126-7d1a-9a53-472b6a434bfd" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019e40ee-b126-71cc-b347-7550399a24ff" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019e40ee-b126-71cc-b347-7550399a24ff_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019e40ee-b126-71cc-b347-7550399a24ff" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019e40ee-b126-71cc-b347-7550399a24ff_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019e40ee-b126-7a0a-9d57-d8b99051bc7b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019e40ee-b126-71cc-b347-7550399a24ff" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019e40ee-b126-7a0a-9d57-d8b99051bc7b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_019e40ee-b126-71fa-a193-97eaa840064d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019e40ee-b126-7a0a-9d57-d8b99051bc7b" xlink:to="loc_us-gaap_ForeignExchangeContractMember_019e40ee-b126-71fa-a193-97eaa840064d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_019e40ee-b126-7a7a-9707-841e526631db" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e40ee-b126-7926-83c9-46ee49411674" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_019e40ee-b126-7a7a-9707-841e526631db" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019e40ee-b126-7548-a64d-c817b49bb897" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019e40ee-b126-7a7a-9707-841e526631db" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_019e40ee-b126-7548-a64d-c817b49bb897" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetFairValueGrossAssetIncludingNotSubjectToMasterNettingArrangement_019e40ee-b126-7b3d-a8a2-241b0877a259" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeAssetFairValueGrossAssetIncludingNotSubjectToMasterNettingArrangement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019e40ee-b126-7a7a-9707-841e526631db" xlink:to="loc_us-gaap_DerivativeAssetFairValueGrossAssetIncludingNotSubjectToMasterNettingArrangement_019e40ee-b126-7b3d-a8a2-241b0877a259" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_019e40ee-b126-767e-8377-8623f11193b9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_019e40ee-b126-7a7a-9707-841e526631db" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_019e40ee-b126-767e-8377-8623f11193b9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_019e40ee-b126-766a-91f7-3299b5d0575b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e40ee-b126-7926-83c9-46ee49411674" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_019e40ee-b126-766a-91f7-3299b5d0575b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityFairValueGrossLiabilityIncludingNotSubjectToMasterNettingArrangement_019e40ee-b126-70d4-838e-f02c884ba045" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeLiabilityFairValueGrossLiabilityIncludingNotSubjectToMasterNettingArrangement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_019e40ee-b126-766a-91f7-3299b5d0575b" xlink:to="loc_us-gaap_DerivativeLiabilityFairValueGrossLiabilityIncludingNotSubjectToMasterNettingArrangement_019e40ee-b126-70d4-838e-f02c884ba045" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_019e40ee-b126-7276-9dc6-843b298a26ae" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_019e40ee-b126-766a-91f7-3299b5d0575b" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosure_019e40ee-b126-7276-9dc6-843b298a26ae" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetCollateralObligationToReturnCashOffset_019e40ee-b126-727f-afa7-cd4ce181b231" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeAssetCollateralObligationToReturnCashOffset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e40ee-b126-7926-83c9-46ee49411674" xlink:to="loc_us-gaap_DerivativeAssetCollateralObligationToReturnCashOffset_019e40ee-b126-727f-afa7-cd4ce181b231" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset_019e40ee-b126-7177-b88c-c899a085e4ba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e40ee-b126-7926-83c9-46ee49411674" xlink:to="loc_us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset_019e40ee-b126-7177-b88c-c899a085e4ba" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/SEGMENTINFORMATIONScheduleofSegmentRevenueSignificantSegmentExpensesandSegmentOperatingEBITDADetails" xlink:type="simple" xlink:href="q-20260630.xsd#SEGMENTINFORMATIONScheduleofSegmentRevenueSignificantSegmentExpensesandSegmentOperatingEBITDADetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/SEGMENTINFORMATIONScheduleofSegmentRevenueSignificantSegmentExpensesandSegmentOperatingEBITDADetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-79da-b52b-b2da89005db5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e40ee-b126-7817-8f4e-e837209b535f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-79da-b52b-b2da89005db5" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e40ee-b126-7817-8f4e-e837209b535f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019e40ee-b126-7466-804b-2b243b3ab331" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e40ee-b126-7817-8f4e-e837209b535f" xlink:to="loc_srt_ConsolidationItemsAxis_019e40ee-b126-7466-804b-2b243b3ab331" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019e40ee-b126-7466-804b-2b243b3ab331_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019e40ee-b126-7466-804b-2b243b3ab331" xlink:to="loc_srt_ConsolidationItemsDomain_019e40ee-b126-7466-804b-2b243b3ab331_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019e40ee-b126-780c-855c-d1b0eb72c9ec" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019e40ee-b126-7466-804b-2b243b3ab331" xlink:to="loc_srt_ConsolidationItemsDomain_019e40ee-b126-780c-855c-d1b0eb72c9ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019e40ee-b126-72be-8082-dfb0244eb9e7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019e40ee-b126-780c-855c-d1b0eb72c9ec" xlink:to="loc_us-gaap_OperatingSegmentsMember_019e40ee-b126-72be-8082-dfb0244eb9e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b126-7c77-a16c-d5887906f466" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e40ee-b126-7817-8f4e-e837209b535f" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b126-7c77-a16c-d5887906f466" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e40ee-b126-7c77-a16c-d5887906f466_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b126-7c77-a16c-d5887906f466" xlink:to="loc_us-gaap_SegmentDomain_019e40ee-b126-7c77-a16c-d5887906f466_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e40ee-b126-73ef-af99-c3d50aed8cd9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b126-7c77-a16c-d5887906f466" xlink:to="loc_us-gaap_SegmentDomain_019e40ee-b126-73ef-af99-c3d50aed8cd9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SemiconductorTechnologiesSegmentMember_019e40ee-b126-7364-bb3b-2a06e460c983" xlink:href="q-20260630.xsd#q_SemiconductorTechnologiesSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e40ee-b126-73ef-af99-c3d50aed8cd9" xlink:to="loc_q_SemiconductorTechnologiesSegmentMember_019e40ee-b126-7364-bb3b-2a06e460c983" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_InterconnectSolutionsSegmentMember_019e40ee-b126-7d16-b265-1f72415129d1" xlink:href="q-20260630.xsd#q_InterconnectSolutionsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e40ee-b126-73ef-af99-c3d50aed8cd9" xlink:to="loc_q_InterconnectSolutionsSegmentMember_019e40ee-b126-7d16-b265-1f72415129d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SegmentRevenueFromContractWithCustomerExcludingAssessedTax_019e40ee-b126-7201-85e8-95d17370ca20" xlink:href="q-20260630.xsd#q_SegmentRevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-79da-b52b-b2da89005db5" xlink:to="loc_q_SegmentRevenueFromContractWithCustomerExcludingAssessedTax_019e40ee-b126-7201-85e8-95d17370ca20" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SegmentCostOfGoodsAndServicesSold_019e40ee-b126-772d-86a7-4d6802f59715" xlink:href="q-20260630.xsd#q_SegmentCostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-79da-b52b-b2da89005db5" xlink:to="loc_q_SegmentCostOfGoodsAndServicesSold_019e40ee-b126-772d-86a7-4d6802f59715" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SegmentSellingGeneralAndAdministrativeExpense_019e40ee-b126-740c-9b01-9d8e8d0493f2" xlink:href="q-20260630.xsd#q_SegmentSellingGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-79da-b52b-b2da89005db5" xlink:to="loc_q_SegmentSellingGeneralAndAdministrativeExpense_019e40ee-b126-740c-9b01-9d8e8d0493f2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SegmentResearchAndDevelopmentExpense_019e40ee-b126-79fb-8f9f-910a23d5fdde" xlink:href="q-20260630.xsd#q_SegmentResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-79da-b52b-b2da89005db5" xlink:to="loc_q_SegmentResearchAndDevelopmentExpense_019e40ee-b126-79fb-8f9f-910a23d5fdde" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SegmentAmortizationOfIntangibleAssetsAndOtherSegmentItems_019e40ee-b126-708b-8dde-90e9af0d7aa9" xlink:href="q-20260630.xsd#q_SegmentAmortizationOfIntangibleAssetsAndOtherSegmentItems"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-79da-b52b-b2da89005db5" xlink:to="loc_q_SegmentAmortizationOfIntangibleAssetsAndOtherSegmentItems_019e40ee-b126-708b-8dde-90e9af0d7aa9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019e40ee-b126-7577-a957-91b018d2be45" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-79da-b52b-b2da89005db5" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019e40ee-b126-7577-a957-91b018d2be45" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SegmentDepreciationAndAmortization_019e40ee-b126-7eb9-9dcc-5c117b65e28e" xlink:href="q-20260630.xsd#q_SegmentDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-79da-b52b-b2da89005db5" xlink:to="loc_q_SegmentDepreciationAndAmortization_019e40ee-b126-7eb9-9dcc-5c117b65e28e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_OperatingIncomeLossBeforeInterestTaxesDepreciationAmortizationForeignExchangeGainsLossesAndSignificantItems_019e40ee-b126-7311-8ffb-79f295ad3ab3" xlink:href="q-20260630.xsd#q_OperatingIncomeLossBeforeInterestTaxesDepreciationAmortizationForeignExchangeGainsLossesAndSignificantItems"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-79da-b52b-b2da89005db5" xlink:to="loc_q_OperatingIncomeLossBeforeInterestTaxesDepreciationAmortizationForeignExchangeGainsLossesAndSignificantItems_019e40ee-b126-7311-8ffb-79f295ad3ab3" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/SEGMENTINFORMATIONScheduleofReconciliationofSegmentOperatingEBITDAtoIncomefromContinuingOperationsBeforeIncomeTaxesDetails" xlink:type="simple" xlink:href="q-20260630.xsd#SEGMENTINFORMATIONScheduleofReconciliationofSegmentOperatingEBITDAtoIncomefromContinuingOperationsBeforeIncomeTaxesDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/SEGMENTINFORMATIONScheduleofReconciliationofSegmentOperatingEBITDAtoIncomefromContinuingOperationsBeforeIncomeTaxesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-7fc5-ab03-4e8321a02894" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e40ee-b126-711b-be28-cd368a1a21e2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-7fc5-ab03-4e8321a02894" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e40ee-b126-711b-be28-cd368a1a21e2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019e40ee-b126-714f-a30e-b7f7f88aa43b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e40ee-b126-711b-be28-cd368a1a21e2" xlink:to="loc_srt_ConsolidationItemsAxis_019e40ee-b126-714f-a30e-b7f7f88aa43b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019e40ee-b126-714f-a30e-b7f7f88aa43b_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019e40ee-b126-714f-a30e-b7f7f88aa43b" xlink:to="loc_srt_ConsolidationItemsDomain_019e40ee-b126-714f-a30e-b7f7f88aa43b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019e40ee-b126-7bef-a2e2-b997144c3842" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019e40ee-b126-714f-a30e-b7f7f88aa43b" xlink:to="loc_srt_ConsolidationItemsDomain_019e40ee-b126-7bef-a2e2-b997144c3842" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019e40ee-b126-7ccd-98d3-186c28497a8d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019e40ee-b126-7bef-a2e2-b997144c3842" xlink:to="loc_us-gaap_OperatingSegmentsMember_019e40ee-b126-7ccd-98d3-186c28497a8d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_019e40ee-b126-7a2a-9566-ccb8102f702c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019e40ee-b126-7bef-a2e2-b997144c3842" xlink:to="loc_us-gaap_CorporateNonSegmentMember_019e40ee-b126-7a2a-9566-ccb8102f702c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b126-7d2d-8ab3-9aefba6dc13a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e40ee-b126-711b-be28-cd368a1a21e2" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b126-7d2d-8ab3-9aefba6dc13a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e40ee-b126-7d2d-8ab3-9aefba6dc13a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b126-7d2d-8ab3-9aefba6dc13a" xlink:to="loc_us-gaap_SegmentDomain_019e40ee-b126-7d2d-8ab3-9aefba6dc13a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e40ee-b126-77f8-afd7-129f21f7214c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b126-7d2d-8ab3-9aefba6dc13a" xlink:to="loc_us-gaap_SegmentDomain_019e40ee-b126-77f8-afd7-129f21f7214c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SemiconductorTechnologiesSegmentMember_019e40ee-b126-761b-a29b-f62a12c121bc" xlink:href="q-20260630.xsd#q_SemiconductorTechnologiesSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e40ee-b126-77f8-afd7-129f21f7214c" xlink:to="loc_q_SemiconductorTechnologiesSegmentMember_019e40ee-b126-761b-a29b-f62a12c121bc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_InterconnectSolutionsSegmentMember_019e40ee-b126-72d9-88e6-db2402f4889e" xlink:href="q-20260630.xsd#q_InterconnectSolutionsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e40ee-b126-77f8-afd7-129f21f7214c" xlink:to="loc_q_InterconnectSolutionsSegmentMember_019e40ee-b126-72d9-88e6-db2402f4889e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_OperatingIncomeLossBeforeInterestTaxesDepreciationAmortizationForeignExchangeGainsLossesAndSignificantItems_019e40ee-b126-7fe3-9936-debbf218208b" xlink:href="q-20260630.xsd#q_OperatingIncomeLossBeforeInterestTaxesDepreciationAmortizationForeignExchangeGainsLossesAndSignificantItems"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-7fc5-ab03-4e8321a02894" xlink:to="loc_q_OperatingIncomeLossBeforeInterestTaxesDepreciationAmortizationForeignExchangeGainsLossesAndSignificantItems_019e40ee-b126-7fe3-9936-debbf218208b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_019e40ee-b126-7b41-81cc-97991850298c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-7fc5-ab03-4e8321a02894" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_019e40ee-b126-7b41-81cc-97991850298c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_InvestmentIncomeInterestExcludingEarningsOnEmployeeRelationCredit_019e40ee-b126-7096-9483-119ab1a17b71" xlink:href="q-20260630.xsd#q_InvestmentIncomeInterestExcludingEarningsOnEmployeeRelationCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-7fc5-ab03-4e8321a02894" xlink:to="loc_q_InvestmentIncomeInterestExcludingEarningsOnEmployeeRelationCredit_019e40ee-b126-7096-9483-119ab1a17b71" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_InterestAndDebtExpenseIncludedInNonoperatingIncomeExpense_019e40ee-b126-728a-85d5-96cef84bbdde" xlink:href="q-20260630.xsd#q_InterestAndDebtExpenseIncludedInNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-7fc5-ab03-4e8321a02894" xlink:to="loc_q_InterestAndDebtExpenseIncludedInNonoperatingIncomeExpense_019e40ee-b126-728a-85d5-96cef84bbdde" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionAndOtherPostretirementBenefitExpense_019e40ee-b126-71dc-a842-c8026b66c011" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PensionAndOtherPostretirementBenefitExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-7fc5-ab03-4e8321a02894" xlink:to="loc_us-gaap_PensionAndOtherPostretirementBenefitExpense_019e40ee-b126-71dc-a842-c8026b66c011" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_ForeignCurrencyTransactionGainLossBeforeTaxExcludingSignificantItems_019e40ee-b126-786d-bacd-2a3aa9ebd736" xlink:href="q-20260630.xsd#q_ForeignCurrencyTransactionGainLossBeforeTaxExcludingSignificantItems"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-7fc5-ab03-4e8321a02894" xlink:to="loc_q_ForeignCurrencyTransactionGainLossBeforeTaxExcludingSignificantItems_019e40ee-b126-786d-bacd-2a3aa9ebd736" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_FutureReimbursableIndirectCostsRelatedToBusinessDivestiture_019e40ee-b126-7c61-bd93-9cb182705f7f" xlink:href="q-20260630.xsd#q_FutureReimbursableIndirectCostsRelatedToBusinessDivestiture"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-7fc5-ab03-4e8321a02894" xlink:to="loc_q_FutureReimbursableIndirectCostsRelatedToBusinessDivestiture_019e40ee-b126-7c61-bd93-9cb182705f7f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonrecurringIncomeExpense_019e40ee-b126-7af3-8da3-12dcc47161bb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherNonrecurringIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-7fc5-ab03-4e8321a02894" xlink:to="loc_us-gaap_OtherNonrecurringIncomeExpense_019e40ee-b126-7af3-8da3-12dcc47161bb" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019e40ee-b126-7dc5-8eb8-7b1326dd7eb7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-7fc5-ab03-4e8321a02894" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019e40ee-b126-7dc5-8eb8-7b1326dd7eb7" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/SEGMENTINFORMATIONScheduleofSignificantItemsbySegmentDetails" xlink:type="simple" xlink:href="q-20260630.xsd#SEGMENTINFORMATIONScheduleofSignificantItemsbySegmentDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/SEGMENTINFORMATIONScheduleofSignificantItemsbySegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-72e8-890b-188e4a49e528" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e40ee-b126-7dc5-83e7-a405f932a52a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-72e8-890b-188e4a49e528" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e40ee-b126-7dc5-83e7-a405f932a52a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019e40ee-b126-7163-b553-70881aabe511" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e40ee-b126-7dc5-83e7-a405f932a52a" xlink:to="loc_srt_ConsolidationItemsAxis_019e40ee-b126-7163-b553-70881aabe511" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019e40ee-b126-7163-b553-70881aabe511_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019e40ee-b126-7163-b553-70881aabe511" xlink:to="loc_srt_ConsolidationItemsDomain_019e40ee-b126-7163-b553-70881aabe511_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019e40ee-b126-71a0-9f2d-094cea0fdedc" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019e40ee-b126-7163-b553-70881aabe511" xlink:to="loc_srt_ConsolidationItemsDomain_019e40ee-b126-71a0-9f2d-094cea0fdedc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019e40ee-b126-7e26-9211-eedf24eb5737" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019e40ee-b126-71a0-9f2d-094cea0fdedc" xlink:to="loc_us-gaap_OperatingSegmentsMember_019e40ee-b126-7e26-9211-eedf24eb5737" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_019e40ee-b126-7db4-b435-29bfb85c5a93" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019e40ee-b126-71a0-9f2d-094cea0fdedc" xlink:to="loc_us-gaap_CorporateNonSegmentMember_019e40ee-b126-7db4-b435-29bfb85c5a93" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b126-7350-82a4-520477fa447b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e40ee-b126-7dc5-83e7-a405f932a52a" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b126-7350-82a4-520477fa447b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e40ee-b126-7350-82a4-520477fa447b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b126-7350-82a4-520477fa447b" xlink:to="loc_us-gaap_SegmentDomain_019e40ee-b126-7350-82a4-520477fa447b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e40ee-b126-7326-827e-01f167583787" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b126-7350-82a4-520477fa447b" xlink:to="loc_us-gaap_SegmentDomain_019e40ee-b126-7326-827e-01f167583787" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SemiconductorTechnologiesSegmentMember_019e40ee-b126-7a85-b5ec-027cf089c5db" xlink:href="q-20260630.xsd#q_SemiconductorTechnologiesSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e40ee-b126-7326-827e-01f167583787" xlink:to="loc_q_SemiconductorTechnologiesSegmentMember_019e40ee-b126-7a85-b5ec-027cf089c5db" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_InterconnectSolutionsSegmentMember_019e40ee-b126-78ed-9201-08eb843b0c11" xlink:href="q-20260630.xsd#q_InterconnectSolutionsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e40ee-b126-7326-827e-01f167583787" xlink:to="loc_q_InterconnectSolutionsSegmentMember_019e40ee-b126-78ed-9201-08eb843b0c11" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_TransformationIntegrationAndOtherCharges_019e40ee-b126-771c-82e3-ba541ee42916" xlink:href="q-20260630.xsd#q_TransformationIntegrationAndOtherCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-72e8-890b-188e4a49e528" xlink:to="loc_q_TransformationIntegrationAndOtherCharges_019e40ee-b126-771c-82e3-ba541ee42916" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnDispositionOfAssets1_019f8385-1cdb-7f27-9855-b3b734e5e40b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossOnDispositionOfAssets1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-72e8-890b-188e4a49e528" xlink:to="loc_us-gaap_GainLossOnDispositionOfAssets1_019f8385-1cdb-7f27-9855-b3b734e5e40b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_EmployeeRetentionCredit_019e40ee-b126-781d-805d-75103f2e6300" xlink:href="q-20260630.xsd#q_EmployeeRetentionCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-72e8-890b-188e4a49e528" xlink:to="loc_q_EmployeeRetentionCredit_019e40ee-b126-781d-805d-75103f2e6300" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonrecurringIncomeExpense_019e40ee-b126-7cc9-b355-8a7821fae1eb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherNonrecurringIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-72e8-890b-188e4a49e528" xlink:to="loc_us-gaap_OtherNonrecurringIncomeExpense_019e40ee-b126-7cc9-b355-8a7821fae1eb" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/SEGMENTINFORMATIONScheduleofSegmentandCorporateInformationDetails" xlink:type="simple" xlink:href="q-20260630.xsd#SEGMENTINFORMATIONScheduleofSegmentandCorporateInformationDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/SEGMENTINFORMATIONScheduleofSegmentandCorporateInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-77d0-861b-ac5b8eaff910" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e40ee-b126-7f8a-829c-560b3e3d67a3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-77d0-861b-ac5b8eaff910" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e40ee-b126-7f8a-829c-560b3e3d67a3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019e40ee-b126-791d-89a9-a112ccba7b2a" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e40ee-b126-7f8a-829c-560b3e3d67a3" xlink:to="loc_srt_ConsolidationItemsAxis_019e40ee-b126-791d-89a9-a112ccba7b2a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019e40ee-b126-791d-89a9-a112ccba7b2a_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019e40ee-b126-791d-89a9-a112ccba7b2a" xlink:to="loc_srt_ConsolidationItemsDomain_019e40ee-b126-791d-89a9-a112ccba7b2a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019e40ee-b126-7506-b432-dca7ad7f86aa" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019e40ee-b126-791d-89a9-a112ccba7b2a" xlink:to="loc_srt_ConsolidationItemsDomain_019e40ee-b126-7506-b432-dca7ad7f86aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019e40ee-b126-7d10-9938-633688267afa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019e40ee-b126-7506-b432-dca7ad7f86aa" xlink:to="loc_us-gaap_OperatingSegmentsMember_019e40ee-b126-7d10-9938-633688267afa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_019e40ee-b126-7b14-b3c1-03a52adc0e93" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019e40ee-b126-7506-b432-dca7ad7f86aa" xlink:to="loc_us-gaap_CorporateNonSegmentMember_019e40ee-b126-7b14-b3c1-03a52adc0e93" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b126-78ed-9052-bc084981024c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e40ee-b126-7f8a-829c-560b3e3d67a3" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b126-78ed-9052-bc084981024c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e40ee-b126-78ed-9052-bc084981024c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b126-78ed-9052-bc084981024c" xlink:to="loc_us-gaap_SegmentDomain_019e40ee-b126-78ed-9052-bc084981024c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e40ee-b126-7d9b-a5e9-5b6bab5f7148" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b126-78ed-9052-bc084981024c" xlink:to="loc_us-gaap_SegmentDomain_019e40ee-b126-7d9b-a5e9-5b6bab5f7148" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SemiconductorTechnologiesSegmentMember_019e40ee-b126-739d-a005-b3dc030a5794" xlink:href="q-20260630.xsd#q_SemiconductorTechnologiesSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e40ee-b126-7d9b-a5e9-5b6bab5f7148" xlink:to="loc_q_SemiconductorTechnologiesSegmentMember_019e40ee-b126-739d-a005-b3dc030a5794" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_InterconnectSolutionsSegmentMember_019e40ee-b126-7877-badd-e06cb02350a9" xlink:href="q-20260630.xsd#q_InterconnectSolutionsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e40ee-b126-7d9b-a5e9-5b6bab5f7148" xlink:to="loc_q_InterconnectSolutionsSegmentMember_019e40ee-b126-7877-badd-e06cb02350a9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019e40ee-b126-77f1-8eaa-73c86dfead46" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-77d0-861b-ac5b8eaff910" xlink:to="loc_us-gaap_Assets_019e40ee-b126-77f1-8eaa-73c86dfead46" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_019e40ee-b126-79f8-8f0e-775b50d0a89e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-77d0-861b-ac5b8eaff910" xlink:to="loc_us-gaap_EquityMethodInvestments_019e40ee-b126-79f8-8f0e-775b50d0a89e" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.qnityelectronics.com/role/SEGMENTINFORMATIONScheduleofCapitalExpenditureReconciliationtoUnauditedInterimConsolidatedFinancialStatementsDetails" xlink:type="simple" xlink:href="q-20260630.xsd#SEGMENTINFORMATIONScheduleofCapitalExpenditureReconciliationtoUnauditedInterimConsolidatedFinancialStatementsDetails"/>
  <link:definitionLink xlink:role="http://www.qnityelectronics.com/role/SEGMENTINFORMATIONScheduleofCapitalExpenditureReconciliationtoUnauditedInterimConsolidatedFinancialStatementsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-72f1-a89c-35b010779080" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e40ee-b126-7c30-8dd0-ba92d9191a5d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-72f1-a89c-35b010779080" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e40ee-b126-7c30-8dd0-ba92d9191a5d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019e40ee-b126-7c8f-b7d1-2a787706c664" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e40ee-b126-7c30-8dd0-ba92d9191a5d" xlink:to="loc_srt_ConsolidationItemsAxis_019e40ee-b126-7c8f-b7d1-2a787706c664" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019e40ee-b126-7c8f-b7d1-2a787706c664_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019e40ee-b126-7c8f-b7d1-2a787706c664" xlink:to="loc_srt_ConsolidationItemsDomain_019e40ee-b126-7c8f-b7d1-2a787706c664_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019e40ee-b126-75e2-a053-9c3c384312c3" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019e40ee-b126-7c8f-b7d1-2a787706c664" xlink:to="loc_srt_ConsolidationItemsDomain_019e40ee-b126-75e2-a053-9c3c384312c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_019e40ee-b126-794e-b243-9e341f83a567" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019e40ee-b126-75e2-a053-9c3c384312c3" xlink:to="loc_us-gaap_OperatingSegmentsMember_019e40ee-b126-794e-b243-9e341f83a567" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_019e40ee-b126-7c32-b68a-279f8dc159f6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019e40ee-b126-75e2-a053-9c3c384312c3" xlink:to="loc_us-gaap_CorporateNonSegmentMember_019e40ee-b126-7c32-b68a-279f8dc159f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b126-7627-8459-5250b7743153" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019e40ee-b126-7c30-8dd0-ba92d9191a5d" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b126-7627-8459-5250b7743153" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e40ee-b126-7627-8459-5250b7743153_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b126-7627-8459-5250b7743153" xlink:to="loc_us-gaap_SegmentDomain_019e40ee-b126-7627-8459-5250b7743153_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e40ee-b126-7574-84c8-e0cbd1629904" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e40ee-b126-7627-8459-5250b7743153" xlink:to="loc_us-gaap_SegmentDomain_019e40ee-b126-7574-84c8-e0cbd1629904" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_SemiconductorTechnologiesSegmentMember_019e40ee-b126-78e3-86da-59875c4fd33c" xlink:href="q-20260630.xsd#q_SemiconductorTechnologiesSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e40ee-b126-7574-84c8-e0cbd1629904" xlink:to="loc_q_SemiconductorTechnologiesSegmentMember_019e40ee-b126-78e3-86da-59875c4fd33c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_InterconnectSolutionsSegmentMember_019e40ee-b126-7728-933b-039fdf90a7fa" xlink:href="q-20260630.xsd#q_InterconnectSolutionsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e40ee-b126-7574-84c8-e0cbd1629904" xlink:to="loc_q_InterconnectSolutionsSegmentMember_019e40ee-b126-7728-933b-039fdf90a7fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentExpenditureAdditionToLongLivedAssets_019e40ee-b126-733c-82f7-dae17ee7cf9e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentExpenditureAdditionToLongLivedAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-72f1-a89c-35b010779080" xlink:to="loc_us-gaap_SegmentExpenditureAdditionToLongLivedAssets_019e40ee-b126-733c-82f7-dae17ee7cf9e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_IncrementalCashSpentOrUnpaidOnCapitalExpenditures_019e40ee-b126-700a-a171-691180b1ce1a" xlink:href="q-20260630.xsd#q_IncrementalCashSpentOrUnpaidOnCapitalExpenditures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-72f1-a89c-35b010779080" xlink:to="loc_q_IncrementalCashSpentOrUnpaidOnCapitalExpenditures_019e40ee-b126-700a-a171-691180b1ce1a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_q_ExpenditureAdditionToLongLivedAssetsNet_019e40ee-b126-78ea-bc85-cdf6d50b6bf8" xlink:href="q-20260630.xsd#q_ExpenditureAdditionToLongLivedAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019e40ee-b126-72f1-a89c-35b010779080" xlink:to="loc_q_ExpenditureAdditionToLongLivedAssetsNet_019e40ee-b126-78ea-bc85-cdf6d50b6bf8" xlink:type="arc" order="2"/>
  </link:definitionLink>
</link:linkbase>
