As filed with the Securities and Exchange Commission on September 19, 2017.

Registration Nos. 333-89661

811-09645

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

Form N-1A

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933	☒
Pre-Effective Amendment No. ____	☐
Post-Effective Amendment No. 171	☒

and/or

REGISTRATION STATEMENT

UNDER

THE INVESTMENT COMPANY ACT OF 1940	☒
Amendment No. 172	☒

(Check Appropriate Box or Boxes)

COLUMBIA FUNDS SERIES TRUST

(Exact Name of Registrant as Specified in Charter)

225 Franklin Street, Boston, Massachusetts 02110

(Address of Principal Executive Officers) (Zip Code)

Registrant’s Telephone Number, Including Area Code: (800) 345-6611

Christopher O. Petersen, Esq.

c/o Columbia Management Investment Advisers, LLC

225 Franklin Street

Boston, Massachusetts 02110

(Name and Address of Agent for Service)

Approximate Date of Proposed Public Offering:

It is proposed that this filing will become effective (check appropriate box)

☒ Immediately upon filing pursuant to paragraph (b)

☐ On (date) pursuant to paragraph (b)

☐ 60 days after filing pursuant to paragraph (a)(1)

☐ On (date) pursuant to paragraph (a)(1)

☐ 75 days after filing pursuant to paragraph (a)(2)

☐ On (date) pursuant to paragraph (a)(2) of rule 485.

If appropriate, check the following box:

☐ This post-effective amendment designates a new effective date for a previously filed post-effective amendment.

This Post-Effective Amendment relates solely to the Registrant’s Columbia AMT-Free California Intermediate Muni Bond Fund, Columbia AMT-Free Georgia Intermediate Muni Bond Fund, Columbia AMT-Free Maryland Intermediate Muni Bond Fund, Columbia AMT-Free North Carolina Intermediate Muni Bond Fund, Columbia AMT-Free South Carolina Intermediate Muni Bond Fund, Columbia AMT-Free Virginia Intermediate Muni Bond Fund and Columbia Short Term Municipal Bond Fund series. Information contained in the Registrant’s Registration Statement relating to any other series of the Registrant is neither amended nor superseded hereby.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933 and the Investment Company Act of 1940, the Registrant, COLUMBIA FUNDS SERIES TRUST, certifies that it meets all of the requirements for effectiveness of this Amendment to its Registration Statement under Rule 485(b) under the Securities Act of 1933 and has duly caused this Amendment to its Registration Statement to be signed on its behalf by the undersigned, duly authorized, in the City of Minneapolis, and The State of Minnesota on the 19th day of September, 2017.

COLUMBIA FUNDS SERIES TRUST
By:	/s/ Christopher O. Petersen
	Christopher O. Petersen
	President

Pursuant to the requirements of the Securities Act of 1933, this Amendment to the Registration Statement has been signed below by the following persons in the capacities indicated on the 19th day of September, 2017.

Signature	Capacity	Signature	Capacity
/s/ Christopher O. Petersen Christopher O. Petersen	President (Principal Executive Officer)	/s/ Patricia M. Flynn* Patricia M. Flynn	Trustee
/s/ Michael G. Clarke* Michael G. Clarke	Chief Financial Officer (Principal Financial Officer) Chief Accounting Officer (Principal Accounting Officer)	/s/ Catherine James Paglia* Catherine James Paglia	Trustee
/s/ William A. Hawkins* William A. Hawkins	Chair of the Board	/s/ Anthony M. Santomero* Anthony M. Santomero	Trustee
/s/ George S. Batejan* George S. Batejan	Trustee	/s/ Minor M. Shaw* Minor M. Shaw	Trustee
/s/ Kathleen A. Blatz* Kathleen A. Blatz	Trustee	/s/ John G. Taft* John G. Taft	Trustee
/s/ Edward J. Boudreau, Jr.* Edward J. Boudreau, Jr.	Trustee	/s/ Alison Taunton-Rigby* Alison Taunton-Rigby	Trustee
/s/ Pamela G. Carlton* Pamela G. Carlton	Trustee	/s/ William F. Truscott* William F. Truscott	Trustee
/s/ William P. Carmichael* William P. Carmichael	Trustee

*	By:	/s/ Joseph D’Alessandro
	Name:	Joseph D’Alessandro**
		Attorney-in-fact
**	Executed by Joseph D’Alessandro on behalf of Michael G. Clarke pursuant to a Power of Attorney, dated May 23, 2016, and incorporated by reference to Post-Effective Amendment No. 154 to Registration Statement No. 333-89661 of the Registrant on Form N-1A (Exhibit (q)(2)), filed with the Commission on May 27, 2016, and on behalf of each of the Trustees pursuant to a Trustees’ Power of Attorney dated February 2, 2017, and incorporated by reference to Post-Effective Amendment No. 164 to Registration Statement No. 333-89661 of the Registrant on Form N-1A (Exhibit (q)(1)), filed with the Commission on May 30, 2017 .

Exhibit Index

Exhibit No.	Description
EX-101.INS	XBRL Instance Document
EX-101.SCH	XBRL Taxonomy Extension Schema Document
EX-101.CAL	XBRL Taxonomy Extension Calculation Linkbase
EX-101.DEF	XBRL Taxonomy Extension Definition Linkbase
EX-101.LAB	XBRL Taxonomy Extension Labels Linkbase
EX-101.PRE	XBRL Taxonomy Extension Presentation Linkbase