<SEC-DOCUMENT>0001127602-18-005985.txt : 20180214
<SEC-HEADER>0001127602-18-005985.hdr.sgml : 20180214
<ACCEPTANCE-DATETIME>20180214141429
ACCESSION NUMBER:		0001127602-18-005985
CONFORMED SUBMISSION TYPE:	5
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20171231
FILED AS OF DATE:		20180214
DATE AS OF CHANGE:		20180214

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			HABERFIELD PATRICK J
		CENTRAL INDEX KEY:			0001493553

	FILING VALUES:
		FORM TYPE:		5
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-12508
		FILM NUMBER:		18610839

	MAIL ADDRESS:	
		STREET 1:		C/O S&T BANK ACCOUNTING DEPT
		STREET 2:		800 PHILADELPHIA ST
		CITY:			INDIANA
		STATE:			PA
		ZIP:			15701

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			S&T BANCORP INC
		CENTRAL INDEX KEY:			0000719220
		STANDARD INDUSTRIAL CLASSIFICATION:	STATE COMMERCIAL BANKS [6022]
		IRS NUMBER:				251434426
		STATE OF INCORPORATION:			PA
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		800 PHILADELPHIA STREET
		STREET 2:		PO BOX 190
		CITY:			INDIANA
		STATE:			PA
		ZIP:			15701
		BUSINESS PHONE:		724-427-2347

	MAIL ADDRESS:	
		STREET 1:		800 PHILADELPHIA STREET
		STREET 2:		PO BOX 190
		CITY:			INDIANA
		STATE:			PA
		ZIP:			15701
</SEC-HEADER>
<DOCUMENT>
<TYPE>5
<SEQUENCE>1
<FILENAME>form5.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>5</documentType>

    <periodOfReport>2017-12-31</periodOfReport>

    <form3HoldingsReported>0</form3HoldingsReported>

    <form4TransactionsReported>0</form4TransactionsReported>

    <issuer>
        <issuerCik>0000719220</issuerCik>
        <issuerName>S&amp;T BANCORP INC</issuerName>
        <issuerTradingSymbol>STBA</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001493553</rptOwnerCik>
            <rptOwnerName>HABERFIELD PATRICK J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>800 PHILADELPHIA ST.</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>INDIANA</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>15701</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>Sr. Executive Vice President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2017-12-31</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>5</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>94.406</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>39.81</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>14339.761</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Increase due to reinvested dividends in a dividend reinvestment plan.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Timothy P. McKee POA for Patrick J. Haberfield</signatureName>
        <signatureDate>2018-02-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
