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        <filer>
          <filerCredentials>
            <cik>0001846709</cik>
            <ccc>XXXXXXXX</ccc>
          </filerCredentials>
        </filer>
        <liveTestFlag>LIVE</liveTestFlag>
  
  
  
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      <issuerInfo>
        <issuerCik>0001835830</issuerCik>
        <issuerName>Klaviyo, Inc.</issuerName>
        <secFileNumber>001-41806</secFileNumber>
        <issuerAddress>
          <com:street1>125 SUMMER STREET, FLOOR 6</com:street1>
          <com:city>BOSTON</com:city>
          <com:stateOrCountry>MA</com:stateOrCountry>
          <com:zipCode>02110</com:zipCode>
        </issuerAddress>
        <issuerContactPhone>800-338-1744</issuerContactPhone>
        <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>SUMMIT INVESTORS GE IX/VC IV (UK), L.P.</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
        <relationshipsToIssuer>
          <relationshipToIssuer>Director</relationshipToIssuer>
          <relationshipToIssuer>10% Stockholder</relationshipToIssuer>
        </relationshipsToIssuer>
      </issuerInfo>
      <securitiesInformation>
        <securitiesClassTitle>Klaviyo, Inc. Class A</securitiesClassTitle>
        <brokerOrMarketmakerDetails>
          <name>Merrill Lynch</name>
          <address>
            <com:street1>555 California Street</com:street1>
            <com:street2>Suite 1800</com:street2>
            <com:city>San Francisco</com:city>
            <com:stateOrCountry>CA</com:stateOrCountry>
            <com:zipCode>94104</com:zipCode>
          </address>
        </brokerOrMarketmakerDetails>
        <noOfUnitsSold>403</noOfUnitsSold>
        <aggregateMarketValue>13000.00</aggregateMarketValue>
        <noOfUnitsOutstanding>72592767</noOfUnitsOutstanding>
        <approxSaleDate>08/16/2024</approxSaleDate>
        <securitiesExchangeName>NYSE</securitiesExchangeName>
      </securitiesInformation>
      <securitiesToBeSold>
        <securitiesClassTitle>Klaviyo, Inc. Class A</securitiesClassTitle>
        <acquiredDate>05/10/2021</acquiredDate>
        <natureOfAcquisitionTransaction>Private Placement</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>403</amountOfSecuritiesAcquired>
        <paymentDate>05/10/2021</paymentDate>
        <natureOfPayment>Cash</natureOfPayment>
      </securitiesToBeSold>
      <nothingToReportFlagOnSecuritiesSoldInPast3Months>Y</nothingToReportFlagOnSecuritiesSoldInPast3Months>
      <remarks>Acquisitions occurred 3/22/19, 12/8/20, 5/10/21
  </remarks>
      <noticeSignature>
        <noticeDate>08/16/2024</noticeDate>
        <signature>Adam Hennessey</signature>
      </noticeSignature>
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text: 144
  0001846709
  XXXXXXXX
  LIVE
  0001835830
  Klaviyo, Inc.
  001-41806
  125 SUMMER STREET, FLOOR 6
  BOSTON
  MA
  02110
  800-338-1744
  SUMMIT INVESTORS GE IX/VC IV (UK), L.P.
  Director
  10% Stockholder
  Klaviyo, Inc. Class A
  Merrill Lynch
  555 California Street
  Suite 1800
  San Francisco
  CA
  94104
  403
  13000.00
  72592767
  08/16/2024
  NYSE
  Klaviyo, Inc. Class A
  05/10/2021
  Private Placement
  Issuer
  N
  403
  05/10/2021
  Cash
  Y
  Acquisitions occurred 3/22/19, 12/8/20, 5/10/21
  08/16/2024
  Adam Hennessey