<SEC-DOCUMENT>0001209191-17-006278.txt : 20170131
<SEC-HEADER>0001209191-17-006278.hdr.sgml : 20170131
<ACCEPTANCE-DATETIME>20170131113520
ACCESSION NUMBER:		0001209191-17-006278
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20170130
FILED AS OF DATE:		20170131
DATE AS OF CHANGE:		20170131

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			UNITIL CORP
		CENTRAL INDEX KEY:			0000755001
		STANDARD INDUSTRIAL CLASSIFICATION:	ELECTRIC & OTHER SERVICES COMBINED [4931]
		IRS NUMBER:				020381573
		STATE OF INCORPORATION:			NH
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		6 LIBERTY LANE WEST
		CITY:			HAMPTON
		STATE:			NH
		ZIP:			03842
		BUSINESS PHONE:		6037736504

	MAIL ADDRESS:	
		STREET 1:		6 LIBERTY LANE WEST
		CITY:			HAMPTON
		STATE:			NH
		ZIP:			03842

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BLACK TODD R
		CENTRAL INDEX KEY:			0001241000

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-08858
		FILM NUMBER:		17559946

	MAIL ADDRESS:	
		STREET 1:		6 LIBERTY LANE WEST
		CITY:			HAMPTON
		STATE:			NH
		ZIP:			03842
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc4.xml
<DESCRIPTION>FORM 4 SUBMISSION
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-01-30</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000755001</issuerCik>
        <issuerName>UNITIL CORP</issuerName>
        <issuerTradingSymbol>UTL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001241000</rptOwnerCik>
            <rptOwnerName>BLACK TODD R</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>6 LIBERTY LANE WEST</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>HAMPTON</rptOwnerCity>
            <rptOwnerState>NH</rptOwnerState>
            <rptOwnerZipCode>03842</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Vice President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common stock, no par value.</value>
            </securityTitle>
            <transactionDate>
                <value>2017-01-30</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1880</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>21263.871</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common stock, no par value.</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2792.43</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Held in trust.</value>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Shares were granted pursuant to the Unitil Corporation Restricted Stock Plan.  Shares will vest 25% per year over four years from date of grant.  Shares will be valued at current market price on date of vesting.</footnote>
        <footnote id="F2">Includes 163.270 shares of common stock acquired on February 26, 2016, 165.810 shares of common stock acquired on May 27, 2016, 165.540 shares of common stock acquired on August 26, 2016 and 153.294 shares of common stock acquired on November 28, 2016, in each case resulting from the reinvestment of dividends pursuant to Unitil Corporation's Dividend Reinvestment and Stock Purchase Plan.</footnote>
        <footnote id="F3">Shares are held in trust under the terms of the Unitil Corporation Tax Deferred Savings and Investment Plan.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Todd R. Black</signatureName>
        <signatureDate>2017-01-31</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
