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 has a population of 1,257 (31 August 2024), which make it the smallest municipality in Satakunta in terms of population. 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). The population density is 3 inhabitants per square kilometre (7.8/sq mi) (31 August 2024). The municipal manager of Siikainen is Heli Kaskiluoto.
The municipality is unilingually Finnish.
Siikainen hosts a buddhist center Samje and the northernmost Stupa in the world.
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