<SEC-DOCUMENT>0000887343-18-000015.txt : 20180126
<SEC-HEADER>0000887343-18-000015.hdr.sgml : 20180126
<ACCEPTANCE-DATETIME>20180126170340
ACCESSION NUMBER:		0000887343-18-000015
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		2
CONFORMED PERIOD OF REPORT:	20180124
FILED AS OF DATE:		20180126
DATE AS OF CHANGE:		20180126

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Terrano Janine
		CENTRAL INDEX KEY:			0001729329

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-20288
		FILM NUMBER:		18552702

	MAIL ADDRESS:	
		STREET 1:		1301 A STREET
		CITY:			TACOMA
		STATE:			WA
		ZIP:			98402

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			COLUMBIA BANKING SYSTEM INC
		CENTRAL INDEX KEY:			0000887343
		STANDARD INDUSTRIAL CLASSIFICATION:	STATE COMMERCIAL BANKS [6022]
		IRS NUMBER:				911422237
		STATE OF INCORPORATION:			WA
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		1301 A STREET
		CITY:			TACOMA
		STATE:			WA
		ZIP:			98402
		BUSINESS PHONE:		2533051900

	MAIL ADDRESS:	
		STREET 1:		1301 A STREET
		CITY:			TACOMA
		STATE:			WA
		ZIP:			98402
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_151700420537251.xml
<DESCRIPTION>FORM 4
<TEXT>
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<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-01-24</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000887343</issuerCik>
        <issuerName>COLUMBIA BANKING SYSTEM INC</issuerName>
        <issuerTradingSymbol>COLB</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001729329</rptOwnerCik>
            <rptOwnerName>Terrano Janine</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1301 A STREET</rptOwnerStreet1>
            <rptOwnerStreet2>STE 800</rptOwnerStreet2>
            <rptOwnerCity>TACOMA</rptOwnerCity>
            <rptOwnerState>WA</rptOwnerState>
            <rptOwnerZipCode>98402</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common</value>
            </securityTitle>
            <transactionDate>
                <value>2018-01-24</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>834</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>834</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Restricted Stock Award</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Cathleen Dent, attorney-in-fact</signatureName>
        <signatureDate>2018-01-26</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EX-24
<SEQUENCE>2
<FILENAME>ex-24.htm
<DESCRIPTION>POA TERRANO
<TEXT>
<!-- Document created using Workiva -->
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<pre>
POWER OF ATTORNEY / CONFORMING STATEMENT



    This Statement confirms that the undersigned, has authorized and designated Kumi Baruffi, Cathleen Dent and Gabrielle Baldwin each with the full power to act alone, to execute and file on the undersigned's behalf, all Form's 3, 4 and 5 (including any amendments thereto) that the undersigned may be required to file with the U. S. Securities and Exchange Commission as a result of the undersigned's ownership of or transactions in securities of Columbia Banking System, Inc.  The authority of Kumi Baruffi, Cathleen Dent and Gabrielle Baldwin under this Statement shall continue until the undersigned is no longer required to file Forms 3, 4 and 5 with regard to his/her ownership of or transactions in securities of Columbia Banking System, Inc., unless earlier revoked in writing.  The undersigned acknowledges that none of Columbia Banking System, Inc., Kumi Baruffi, Cathleen Dent or Gabrielle Baldwin is assuming any of the undersigned's responsibilities to comply with Section 16 of the Securities and Exchange Act of 1934.

The Power of Attorney shall remain in full force and effect until the undersigned is no longer subject to the reporting requirements of the Securities Exchange Act of 1934 and the rules thereunder, unless earlier revoked by the undersigned in a signed writing delivered to the attorney-in-fact.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be executed as of January 24, 2018

                        Signature: Janine Terrano
</pre>
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</SEC-DOCUMENT>
