<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:ns2="http://www.sec.gov/edgar/common">
    <headerData>
        <submissionType>144</submissionType>
        <filerInfo>
            <filer>
                <filerCredentials>
                    <cik>0001930126</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>MARK R SLICER</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>8th Floor</ns2:street2>
                    <ns2:city>New York</ns2:city>
                    <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                    <ns2:zipCode>10004</ns2:zipCode>
                </address>
            </brokerOrMarketmakerDetails>
            <noOfUnitsSold>519</noOfUnitsSold>
            <aggregateMarketValue>112711.23</aggregateMarketValue>
            <noOfUnitsOutstanding>49275852</noOfUnitsOutstanding>
            <approxSaleDate>06/07/2024</approxSaleDate>
            <securitiesExchangeName>NYSE</securitiesExchangeName>
        </securitiesInformation>
        <securitiesToBeSold>
            <securitiesClassTitle>COMMON</securitiesClassTitle>
            <acquiredDate>02/14/2024</acquiredDate>
            <natureOfAcquisitionTransaction>Restricted Stock</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>ISSUER</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>519</amountOfSecuritiesAcquired>
            <paymentDate>02/14/2024</paymentDate>
            <natureOfPayment>Not Applicable</natureOfPayment>
        </securitiesToBeSold>
        <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
        <securitiesSoldInPast3Months>
            <sellerDetails>
                <name>MARK R SLICER</name>
                <address>
                    <ns2:street1>16 Jonspin Road</ns2:street1>
                    <ns2:city>Wilmington</ns2:city>
                    <ns2:stateOrCountry>MA</ns2:stateOrCountry>
                    <ns2:zipCode>01887</ns2:zipCode>
                </address>
            </sellerDetails>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <saleDate>06/06/2024</saleDate>
            <amountOfSecuritiesSold>519</amountOfSecuritiesSold>
            <grossProceeds>114807.99</grossProceeds>
        </securitiesSoldInPast3Months>
        <noticeSignature>
            <noticeDate>06/07/2024</noticeDate>
            <planAdoptionDates>
                <planAdoptionDate>03/07/2024</planAdoptionDate>
            </planAdoptionDates>
            <signature>/s/ Mark Robert Slicer</signature>
        </noticeSignature>
    </formData>
</edgarSubmission>
[{"type": "144", "sequence": "1", "filename": "primary_doc.xml", "secsgml_size_bytes": 3991}]
144
0001930126
XXXXXXXX
LIVE
0000704532
ONTO INNOVATION INC.
001-39110
16 Jonspin Road
Wilmington
MA
01887
(978) 253-6200
MARK R SLICER
Officer
Common
Morgan Stanley Smith Barney LLC Executive Financial Services
1 New York Plaza
8th Floor
New York
NY
10004
519
112711.23
49275852
06/07/2024
NYSE
COMMON
02/14/2024
Restricted Stock
ISSUER
N
519
02/14/2024
Not Applicable
N
MARK R SLICER
16 Jonspin Road
Wilmington
MA
01887
Common
06/06/2024
519
114807.99
06/07/2024
03/07/2024
/s/ Mark Robert Slicer