Supplement dated September 27, 2024 to the Prospectus, Summary Prospectus and Statement of Additional Information (SAI), each as supplemented, of each of the following funds: 

Fund	Prospectus, Summary Prospectus and SAI Dated
Columbia Acorn Trust
Columbia Acorn Fund	5/1/2024
Columbia Acorn International	5/1/2024
Columbia Acorn International Select	5/1/2024
Columbia Thermostat Fund	5/1/2024

Class S information on each Fund's Prospectus and Summary Prospectus front covers is hereby superseded and replaced with the following:

For Columbia Acorn Fund: 

Class	Ticker Symbol
S(a)	ACRSX

(a)

Class S will be operational on or about October 2, 2024.

For Columbia Acorn International: 

Class	Ticker Symbol
S(a)	CCIDX

(a)

Class S will be operational on or about October 2, 2024.

For Columbia Acorn International Select: 

Class	Ticker Symbol
S(a)	ACFEX

(a)

Class S will be operational on or about October 2, 2024.

For Columbia Thermostat Fund: 

Class	Ticker Symbol
S(a)	COTDX

(a)

Class S will be operational on or about October 2, 2024.

Also Class S information on the front cover of the SAI is hereby superseded and replaced with the following: 

Fund	Class S(a)
Columbia Acorn Fund	ACRSX
Columbia Acorn International	CCIDX
Columbia Acorn International Select	ACFEX
Columbia Thermostat Fund	COTDX

(a)

Class S will be operational on or about October 2, 2024.

Shareholders should retain this Supplement for future reference.

SUP000_00_163_(09/24)