FORM 4
[ ] Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).         
 UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES
                                                                                  
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OMB Number: 3235-0287
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Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940
                      

1. Name and Address of Reporting Person *

Deer Aaron James		 2. Issuer Name and Ticker or Trading Symbol

COLUMBIA BANKING SYSTEM, INC. [ COLB ] 		5. Relationship of Reporting Person(s) to Issuer (Check all applicable)

_____ Director                    _____ 10% Owner
__X__ Officer (give title below)    _____ Other (specify below)
EVP Chief Financial Officer
(Last)          (First)          (Middle)

C/O COLUMBIA BANKING SYSTEM, INC., PO BOX 2156, MS 3100		 3. Date of Earliest Transaction (MM/DD/YYYY)

2/28/2023
(Street)

TACOMA, WA 98401-2156
(City)        (State)        (Zip)
4. If Amendment, Date Original Filed (MM/DD/YYYY)

 
 6. Individual or Joint/Group Filing (Check Applicable Line)

_X _ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3) 		2. Trans. Date 2A. Deemed Execution Date, if any 3. Trans. Code
(Instr. 8) 		4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5) 		5. Amount of Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 3 and 4) 		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4)
Code V Amount (A) or (D) Price
Common 2/28/2023  A  1430 (1)A$0 29705 D  
Common 2/28/2023  A  1430 (1)A$0 31135 D  
Common 2/28/2023  A  2195 (1)A$0 33330 D  
Common 2/28/2023  A  1960 (1)A$0 35290 D  

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivate Security
(Instr. 3)		2. Conversion or Exercise Price of Derivative Security3. Trans. Date3A. Deemed Execution Date, if any4. Trans. Code
(Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date7. Title and Amount of Securities Underlying Derivative Security
(Instr. 3 and 4)		8. Price of Derivative Security
(Instr. 5)		9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)11. Nature of Indirect Beneficial Ownership (Instr. 4)
CodeV(A)(D)Date ExercisableExpiration DateTitleAmount or Number of Shares
Explanation of Responses:
(1) At the effective time of the merger (the "Effective Time") of Cascade Merger Sub, Inc. ("Merger Sub"), a direct, wholly-owned subsidiary of the Issuer, with and into Umpqua Holdings Corporation ("Umpqua"), pursuant to that certain Agreement and Plan of Merger, dated as of October 11, 2021 (the "Merger Agreement"), by and among the Issuer, Umpqua and Merger Sub, each outstanding performance stock unit award of the Issuer granted under the Issuer's equity compensation plans was converted into a restricted stock unit award of the Issuer based on a level of performance determined in accordance with the Merger Agreement, with such awards continuing to vest after the Effective Time solely based on continued service.

Reporting Owners
Reporting Owner Name / Address
Relationships
Director10% OwnerOfficerOther
Deer Aaron James
C/O COLUMBIA BANKING SYSTEM, INC.
PO BOX 2156, MS 3100
TACOMA, WA 98401-2156

EVP Chief Financial Officer
Signatures
/s/ Andrea M. Newburn, Attorney-in-fact3/2/2023
**Signature of Reporting PersonDate
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
*If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note:File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
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Power of Attorney

The undersigned hereby constitutes and appoints Kumi Yamamoto Baruffi, Ronald L. Farnsworth, Neal T. McLaughlin, Andrea M. Newburn and Lisa White as the undersigned's attorneys-in-fact to (1) execute and file for and on behalf of the undersigned, all reports of, and changes in, beneficial ownership by the undersigned of securities of Columbia Banking System, Inc. (the "Company") as may be required by Section 16(a) of the Securities Exchange Act of 1934 and the rules thereunder, and any other forms or reports the undersigned may be required to file in connection with the undersigned's ownership, acquisition, or disposition of securities of the Company, including forms required to generate codes for the Securities and Exchange Commission's electronic filing system; (2) do and perform any and all acts for and on behalf of the undersigned which may be necessary or desirable to complete and execute and file any such reports with the United States Securities and Exchange Commission and any stock exchange or similar authority; and (3) take any other action of any nature whatsoever in connection with the foregoing that, in the opinion of such attorneys-in-fact, may be of benefit to, and in the best interest of, or legally required of, the undersigned.

The undersigned hereby grants to said attorneys-in-fact, each acting alone, full power and authority to do and perform any and every act and thing whatsoever requisite, necessary, or proper to be done in the exercise of any of the rights and powers herein granted, as fully to all intents and purposes as the undersigned might or could do if personally present, with full power of substitution or revocation, hereby ratifying and confirming all that such attorneys-in-fact, or such attorneys-in-facts substitute or substitutes, shall lawfully do or cause to be done by the virtue of this Power of Attorney and the rights and powers herein granted. The undersigned acknowledges that the foregoing attorneys-in-fact, in serving in such capacity at the request of the undersigned, are not assuming, nor is the Company assuming, any of the undersigned's responsibilities to comply with Section 16 of the Securities Exchange Act of 1934.

This Power of Attorney shall remain in full force and effect until the undersigned is no longer required to file reports pursuant to Section 16(a) of the Securities Exchange Act of 1934 and the rules thereunder with respect to the undersigned's holdings of and transactions in securities issued by the Company, unless earlier revoked by the undersigned in a signed writing delivered to the attorneys-in-fact. The undersigned acknowledges that none of the Company, Kumi Yamamoto Baruffi, Ronald L. Farnsworth, Neal T. McLaughlin, Andrea M. Newburn and Lisa White are assuming any of the undersigned's responsibilities to comply with Section 16 of the Securities and Exchange Act of 1934.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be executed as of February 28, 2023.

Signature: /s/ Aaron James Deer
Name: Aaron James Deer

Notarization/Certification
State of Washington County of Pierce

Signed or attested before me on 02/28/2023 by Aaron James Deer.

/s/ Karina Busch
Notary/Agent/Subagent signature

Karina Busch
Notary printed or stamped name

07/01/2024
Notary expiration date