content: <?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:com="http://www.sec.gov/edgar/common">
    <headerData>
      <submissionType>144</submissionType>
      <filerInfo>
        <filer>
          <filerCredentials>
            <cik>0001991400</cik>
            <ccc>XXXXXXXX</ccc>
          </filerCredentials>
        </filer>
        <liveTestFlag>LIVE</liveTestFlag>
  
  
  
      </filerInfo>
    </headerData>
    <formData>
      <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>Chaves Allen</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
        <relationshipsToIssuer>
          <relationshipToIssuer>Officer</relationshipToIssuer>
        </relationshipsToIssuer>
      </issuerInfo>
      <securitiesInformation>
        <securitiesClassTitle>Series A</securitiesClassTitle>
        <brokerOrMarketmakerDetails>
          <name>Fidelity Brokerage Services LLC</name>
          <address>
            <com:street1>900 Salem Street</com:street1>
            <com:city>Smithfield</com:city>
            <com:stateOrCountry>RI</com:stateOrCountry>
            <com:zipCode>02917</com:zipCode>
          </address>
        </brokerOrMarketmakerDetails>
        <noOfUnitsSold>13401</noOfUnitsSold>
        <aggregateMarketValue>462791.47</aggregateMarketValue>
        <noOfUnitsOutstanding>78803963</noOfUnitsOutstanding>
        <approxSaleDate>11/18/2024</approxSaleDate>
        <securitiesExchangeName>NYSE</securitiesExchangeName>
      </securitiesInformation>
      <securitiesToBeSold>
        <securitiesClassTitle>Series A</securitiesClassTitle>
        <acquiredDate>11/15/2024</acquiredDate>
        <natureOfAcquisitionTransaction>Restricted Stock Vesting</natureOfAcquisitionTransaction>
        <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
        <isGiftTransaction>N</isGiftTransaction>
        <amountOfSecuritiesAcquired>13401</amountOfSecuritiesAcquired>
        <paymentDate>11/15/2024</paymentDate>
        <natureOfPayment>Compensation</natureOfPayment>
      </securitiesToBeSold>
      <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
      <securitiesSoldInPast3Months>
        <sellerDetails>
          <name>Allen M. Chaves Jr</name>
          <address>
            <com:street1>125 Summer Street</com:street1>
            <com:street2>6th Floor</com:street2>
            <com:city>Boston</com:city>
            <com:stateOrCountry>MA</com:stateOrCountry>
            <com:zipCode>02110</com:zipCode>
          </address>
        </sellerDetails>
        <securitiesClassTitle>Series A</securitiesClassTitle>
        <saleDate>09/16/2024</saleDate>
        <amountOfSecuritiesSold>130000</amountOfSecuritiesSold>
        <grossProceeds>4140448.00</grossProceeds>
      </securitiesSoldInPast3Months>
      <securitiesSoldInPast3Months>
        <sellerDetails>
          <name>Allen M. Chaves Jr</name>
          <address>
            <com:street1>125 Summer Street</com:street1>
            <com:street2>6th Floor</com:street2>
            <com:city>Boston</com:city>
            <com:stateOrCountry>MA</com:stateOrCountry>
            <com:zipCode>02110</com:zipCode>
          </address>
        </sellerDetails>
        <securitiesClassTitle>Series A</securitiesClassTitle>
        <saleDate>11/11/2024</saleDate>
        <amountOfSecuritiesSold>150000</amountOfSecuritiesSold>
        <grossProceeds>5037900.00</grossProceeds>
      </securitiesSoldInPast3Months>
      <securitiesSoldInPast3Months>
        <sellerDetails>
          <name>Allen M. Chaves Jr</name>
          <address>
            <com:street1>125 Summer Street</com:street1>
            <com:street2>6th Floor</com:street2>
            <com:city>Boston</com:city>
            <com:stateOrCountry>MA</com:stateOrCountry>
            <com:zipCode>02110</com:zipCode>
          </address>
        </sellerDetails>
        <securitiesClassTitle>Series A</securitiesClassTitle>
        <saleDate>11/12/2024</saleDate>
        <amountOfSecuritiesSold>150000</amountOfSecuritiesSold>
        <grossProceeds>5464860.00</grossProceeds>
      </securitiesSoldInPast3Months>
      <securitiesSoldInPast3Months>
        <sellerDetails>
          <name>Allen M. Chaves Jr</name>
          <address>
            <com:street1>125 Summer Street</com:street1>
            <com:street2>6th Floor</com:street2>
            <com:city>Boston</com:city>
            <com:stateOrCountry>MA</com:stateOrCountry>
            <com:zipCode>02110</com:zipCode>
          </address>
        </sellerDetails>
        <securitiesClassTitle>Series A</securitiesClassTitle>
        <saleDate>11/13/2024</saleDate>
        <amountOfSecuritiesSold>42867</amountOfSecuritiesSold>
        <grossProceeds>1590284.25</grossProceeds>
      </securitiesSoldInPast3Months>
      <securitiesSoldInPast3Months>
        <sellerDetails>
          <name>Allen M. Chaves Jr</name>
          <address>
            <com:street1>125 Summer Street</com:street1>
            <com:street2>6th Floor</com:street2>
            <com:city>Boston</com:city>
            <com:stateOrCountry>MA</com:stateOrCountry>
            <com:zipCode>02110</com:zipCode>
          </address>
        </sellerDetails>
        <securitiesClassTitle>Series A</securitiesClassTitle>
        <saleDate>11/14/2024</saleDate>
        <amountOfSecuritiesSold>52035</amountOfSecuritiesSold>
        <grossProceeds>1937570.06</grossProceeds>
      </securitiesSoldInPast3Months>
      <remarks>Sale includes an amount necessary to cover a tax obligation resulting from the settlement of a vested equity award distribution.</remarks>
      <noticeSignature>
        <noticeDate>11/18/2024</noticeDate>
        <signature>/s/Wade Moss, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Allen M Chaves Jr </signature>
      </noticeSignature>
    </formData>
  </edgarSubmission>
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text: 144
  0001991400
  XXXXXXXX
  LIVE
  0001835830
  Klaviyo, Inc.
  001-41806
  125 SUMMER STREET, FLOOR 6
  BOSTON
  MA
  02110
  800-338-1744
  Chaves Allen
  Officer
  Series A
  Fidelity Brokerage Services LLC
  900 Salem Street
  Smithfield
  RI
  02917
  13401
  462791.47
  78803963
  11/18/2024
  NYSE
  Series A
  11/15/2024
  Restricted Stock Vesting
  Issuer
  N
  13401
  11/15/2024
  Compensation
  N
  Allen M. Chaves Jr
  125 Summer Street
  6th Floor
  Boston
  MA
  02110
  Series A
  09/16/2024
  130000
  4140448.00
  Allen M. Chaves Jr
  125 Summer Street
  6th Floor
  Boston
  MA
  02110
  Series A
  11/11/2024
  150000
  5037900.00
  Allen M. Chaves Jr
  125 Summer Street
  6th Floor
  Boston
  MA
  02110
  Series A
  11/12/2024
  150000
  5464860.00
  Allen M. Chaves Jr
  125 Summer Street
  6th Floor
  Boston
  MA
  02110
  Series A
  11/13/2024
  42867
  1590284.25
  Allen M. Chaves Jr
  125 Summer Street
  6th Floor
  Boston
  MA
  02110
  Series A
  11/14/2024
  52035
  1937570.06
  Sale includes an amount necessary to cover a tax obligation resulting from the settlement of a vested equity award distribution.
  11/18/2024
  /s/Wade Moss, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Allen M Chaves Jr