Siikainen (Swedish: Siikais) is a municipality of Finland.

It is located in the former province of Western Finland and is part of the Satakunta region.

The municipality covers an area of 491.33 square kilometres (189.70 sq mi) of which 28.10 square kilometres (10.85 sq mi) is inland water (2018-01-01).

[1] The population density is 3 inhabitants per square kilometre (7.8/sq mi) (31 December 2024).

Siikainen hosts a buddhist center Samje and the northernmost Stupa in the world.