Korsholm (Mustasaari in Finnish) is a municipality of Finland. The city of Vaasa was founded in Korsholm, and today the municipality completely surrounds the city.

It is located in the province of Western Finland and is part of the Ostrobothnia region. The municipality has a population of 17 239 (2003) and covers an area of 3 606 km² of which 2 759 km² is water. The population density is 20.8 inhabitants per km².

The municipality is bilingual, with a majority (73%) being Swedish and a minority (27%) Finnish speakers.

Korsholm has a history that can be dated back to 1348. In that year Korsholm was mentioned for the first time in writing in a royal letter concerning freedom of commerce. Therefore the municipality celebrated its 650th anniversary in 1998. The municipality got its Swedish name from Korsholm Castle (Chrysseborg) from which the whole of Ostrobothnia was governed for hundreds of years.

Finland's longest bridge, the Replot Bridge, can be found in this municipality. It connects the island of Replot (Raippaluoto in Finnish) to the mainland. Finland's second oldest stone bridge that is still in use, can also be found in Korsholm, in the village of Toby (Fi. Tuovila).

The homepage of Korsholm (http://www.korsholm.fi/default.aspx)