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        <filerInfo>
            <filer>
                <filerCredentials>
                    <cik>0001792618</cik>
                    <ccc>XXXXXXXX</ccc>
                </filerCredentials>
            </filer>
            <liveTestFlag>LIVE</liveTestFlag>



        </filerInfo>
    </headerData>
    <formData>
        <issuerInfo>
            <issuerCik>0000704532</issuerCik>
            <issuerName>ONTO INNOVATION INC.</issuerName>
            <secFileNumber>001-39110</secFileNumber>
            <issuerAddress>
                <ns2:street1>16 Jonspin Road</ns2:street1>
                <ns2:city>Wilmington</ns2:city>
                <ns2:stateOrCountry>MA</ns2:stateOrCountry>
                <ns2:zipCode>01887</ns2:zipCode>
            </issuerAddress>
            <issuerContactPhone>(978) 253-6200</issuerContactPhone>
            <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>ROBERT FIORDALICE</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
            <relationshipsToIssuer>
                <relationshipToIssuer>Officer</relationshipToIssuer>
            </relationshipsToIssuer>
        </issuerInfo>
        <securitiesInformation>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <brokerOrMarketmakerDetails>
                <name>Morgan Stanley Smith Barney LLC Executive Financial Services</name>
                <address>
                    <ns2:street1>1 New York Plaza</ns2:street1>
                    <ns2:street2>38th Floor</ns2:street2>
                    <ns2:city>New York</ns2:city>
                    <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                    <ns2:zipCode>10004</ns2:zipCode>
                </address>
            </brokerOrMarketmakerDetails>
            <noOfUnitsSold>7049</noOfUnitsSold>
            <aggregateMarketValue>882420.17</aggregateMarketValue>
            <noOfUnitsOutstanding>49065801</noOfUnitsOutstanding>
            <approxSaleDate>09/15/2023</approxSaleDate>
            <securitiesExchangeName>NYSE</securitiesExchangeName>
        </securitiesInformation>
        <securitiesToBeSold>
            <securitiesClassTitle>COMMON</securitiesClassTitle>
            <acquiredDate>06/02/2019</acquiredDate>
            <natureOfAcquisitionTransaction>Restricted Stock</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>ISSUER</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>609</amountOfSecuritiesAcquired>
            <paymentDate>06/02/2019</paymentDate>
            <natureOfPayment>Not Applicable</natureOfPayment>
        </securitiesToBeSold>
        <securitiesToBeSold>
            <securitiesClassTitle>COMMON</securitiesClassTitle>
            <acquiredDate>05/31/2020</acquiredDate>
            <natureOfAcquisitionTransaction>Restricted Stock</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>ISSUER</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>870</amountOfSecuritiesAcquired>
            <paymentDate>05/31/2020</paymentDate>
            <natureOfPayment>Not Applicable</natureOfPayment>
        </securitiesToBeSold>
        <securitiesToBeSold>
            <securitiesClassTitle>COMMON</securitiesClassTitle>
            <acquiredDate>05/31/2022</acquiredDate>
            <natureOfAcquisitionTransaction>Restricted Stock</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>ISSUER</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>941</amountOfSecuritiesAcquired>
            <paymentDate>05/31/2022</paymentDate>
            <natureOfPayment>Not Applicable</natureOfPayment>
        </securitiesToBeSold>
        <securitiesToBeSold>
            <securitiesClassTitle>COMMON</securitiesClassTitle>
            <acquiredDate>05/31/2021</acquiredDate>
            <natureOfAcquisitionTransaction>Restricted Stock</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>ISSUER</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>950</amountOfSecuritiesAcquired>
            <paymentDate>05/31/2021</paymentDate>
            <natureOfPayment>Not Applicable</natureOfPayment>
        </securitiesToBeSold>
        <securitiesToBeSold>
            <securitiesClassTitle>COMMON</securitiesClassTitle>
            <acquiredDate>02/07/2022</acquiredDate>
            <natureOfAcquisitionTransaction>Performance Shares</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>ISSUER</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>1109</amountOfSecuritiesAcquired>
            <paymentDate>02/07/2022</paymentDate>
            <natureOfPayment>Not Applicable</natureOfPayment>
        </securitiesToBeSold>
        <securitiesToBeSold>
            <securitiesClassTitle>COMMON</securitiesClassTitle>
            <acquiredDate>02/07/2023</acquiredDate>
            <natureOfAcquisitionTransaction>Performance Shares</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>ISSUER</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>1098</amountOfSecuritiesAcquired>
            <paymentDate>02/07/2023</paymentDate>
            <natureOfPayment>Not Applicable</natureOfPayment>
        </securitiesToBeSold>
        <securitiesToBeSold>
            <securitiesClassTitle>COMMON</securitiesClassTitle>
            <acquiredDate>02/07/2021</acquiredDate>
            <natureOfAcquisitionTransaction>Restricted Stock</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>ISSUER</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>352</amountOfSecuritiesAcquired>
            <paymentDate>02/07/2021</paymentDate>
            <natureOfPayment>Not Applicable</natureOfPayment>
        </securitiesToBeSold>
        <securitiesToBeSold>
            <securitiesClassTitle>COMMON</securitiesClassTitle>
            <acquiredDate>02/07/2023</acquiredDate>
            <natureOfAcquisitionTransaction>Restricted Stock</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>ISSUER</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>351</amountOfSecuritiesAcquired>
            <paymentDate>02/07/2023</paymentDate>
            <natureOfPayment>Not Applicable</natureOfPayment>
        </securitiesToBeSold>
        <securitiesToBeSold>
            <securitiesClassTitle>COMMON</securitiesClassTitle>
            <acquiredDate>02/07/2022</acquiredDate>
            <natureOfAcquisitionTransaction>Restricted Stock</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>ISSUER</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>352</amountOfSecuritiesAcquired>
            <paymentDate>02/07/2022</paymentDate>
            <natureOfPayment>Not Applicable</natureOfPayment>
        </securitiesToBeSold>
        <securitiesToBeSold>
            <securitiesClassTitle>COMMON</securitiesClassTitle>
            <acquiredDate>12/31/2020</acquiredDate>
            <natureOfAcquisitionTransaction>Employee Stock Purchase Plan</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>ISSUER</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>417</amountOfSecuritiesAcquired>
            <paymentDate>12/31/2020</paymentDate>
            <natureOfPayment>Cash</natureOfPayment>
        </securitiesToBeSold>
        <nothingToReportFlagOnSecuritiesSoldInPast3Months>Y</nothingToReportFlagOnSecuritiesSoldInPast3Months>
        <noticeSignature>
            <noticeDate>09/15/2023</noticeDate>
            <planAdoptionDates>
                <planAdoptionDate>06/16/2023</planAdoptionDate>
            </planAdoptionDates>
            <signature>/s/ Robert William Fiordalice</signature>
        </noticeSignature>
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144
0001792618
XXXXXXXX
LIVE
0000704532
ONTO INNOVATION INC.
001-39110
16 Jonspin Road
Wilmington
MA
01887
(978) 253-6200
ROBERT FIORDALICE
Officer
Common
Morgan Stanley Smith Barney LLC Executive Financial Services
1 New York Plaza
38th Floor
New York
NY
10004
7049
882420.17
49065801
09/15/2023
NYSE
COMMON
06/02/2019
Restricted Stock
ISSUER
N
609
06/02/2019
Not Applicable
COMMON
05/31/2020
Restricted Stock
ISSUER
N
870
05/31/2020
Not Applicable
COMMON
05/31/2022
Restricted Stock
ISSUER
N
941
05/31/2022
Not Applicable
COMMON
05/31/2021
Restricted Stock
ISSUER
N
950
05/31/2021
Not Applicable
COMMON
02/07/2022
Performance Shares
ISSUER
N
1109
02/07/2022
Not Applicable
COMMON
02/07/2023
Performance Shares
ISSUER
N
1098
02/07/2023
Not Applicable
COMMON
02/07/2021
Restricted Stock
ISSUER
N
352
02/07/2021
Not Applicable
COMMON
02/07/2023
Restricted Stock
ISSUER
N
351
02/07/2023
Not Applicable
COMMON
02/07/2022
Restricted Stock
ISSUER
N
352
02/07/2022
Not Applicable
COMMON
12/31/2020
Employee Stock Purchase Plan
ISSUER
N
417
12/31/2020
Cash
Y
09/15/2023
06/16/2023
/s/ Robert William Fiordalice