<?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>0001610257</cik>
                    <ccc>XXXXXXXX</ccc>
                </filerCredentials>
            </filer>
            <liveTestFlag>LIVE</liveTestFlag>



        </filerInfo>
    </headerData>
    <formData>
        <issuerInfo>
            <issuerCik>0001145986</issuerCik>
            <issuerName>ASPEN AEROGELS, INC.</issuerName>
            <secFileNumber>001-36481</secFileNumber>
            <issuerAddress>
                <ns2:street1>30 FORBES ROAD, BUILDING B,</ns2:street1>
                <ns2:city>NORTHBOROUGH</ns2:city>
                <ns2:stateOrCountry>MA</ns2:stateOrCountry>
                <ns2:zipCode>01532</ns2:zipCode>
            </issuerAddress>
            <issuerContactPhone>5086911111</issuerContactPhone>
            <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>DONALD YOUNG</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
            <relationshipsToIssuer>
                <relationshipToIssuer>Director</relationshipToIssuer>
                <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>691124</noOfUnitsSold>
            <aggregateMarketValue>20505649.08</aggregateMarketValue>
            <noOfUnitsOutstanding>76161210</noOfUnitsOutstanding>
            <approxSaleDate>05/28/2024</approxSaleDate>
            <securitiesExchangeName>NYSE</securitiesExchangeName>
        </securitiesInformation>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>05/28/2024</acquiredDate>
            <natureOfAcquisitionTransaction>Exercise of Stock Options</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>691124</amountOfSecuritiesAcquired>
            <paymentDate>05/28/2024</paymentDate>
            <natureOfPayment>Cash</natureOfPayment>
        </securitiesToBeSold>
        <nothingToReportFlagOnSecuritiesSoldInPast3Months>Y</nothingToReportFlagOnSecuritiesSoldInPast3Months>
        <remarks>The securities to be sold were and will be received upon the exercise of stock options over the next three months. The dates of acquisition and payment were and will be the dates of exercise/sale.</remarks>
        <noticeSignature>
            <noticeDate>05/28/2024</noticeDate>
            <planAdoptionDates>
                <planAdoptionDate>02/26/2024</planAdoptionDate>
            </planAdoptionDates>
            <signature>/s/ Donald R Young</signature>
        </noticeSignature>
    </formData>
</edgarSubmission>
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144
0001610257
XXXXXXXX
LIVE
0001145986
ASPEN AEROGELS, INC.
001-36481
30 FORBES ROAD, BUILDING B,
NORTHBOROUGH
MA
01532
5086911111
DONALD YOUNG
Director
Officer
Common
Morgan Stanley Smith Barney LLC Executive Financial Services
1 New York Plaza
8th Floor
New York
NY
10004
691124
20505649.08
76161210
05/28/2024
NYSE
Common
05/28/2024
Exercise of Stock Options
Issuer
N
691124
05/28/2024
Cash
Y
The securities to be sold were and will be received upon the exercise of stock options over the next three months. The dates of acquisition and payment were and will be the dates of exercise/sale.
05/28/2024
02/26/2024
/s/ Donald R Young