Äetsä is a former municipality of southwestern Finland. The municipality was founded on 1981 when municipalities of Keikyä and Kiikka were consolidated to a single municipality.
On 1 January 2009, it was consolidated with the municipalities of Vammala and Mouhijärvi to form a new city of Sastamala.
Äetsä was located in the western Pirkanmaa region, and was part of the former (1997 to 2010) province of Western Finland.
The municipality was unilingually Finnish.