Askainen (Finnish: [ˈɑskɑi̯nen]; Swedish: Villnäs) is a former municipality of Finland.

It is located in southwestern part of the country in the Varsinais-Suomi region.

The municipality had a population of 938 (2004-12-31) and covered an area of 61.52 km2 (excluding sea) of which 0.26 km2 is inland water.

Askainen was first mentioned in 1374 as Askais, when it was a part of the Nousiainen parish.

Askainen was also held by the monastery of Naantali before the Reformation.