Soini is a municipality of Finland. It is located in the South Ostrobothnia region. The municipality has a population of () and covers an area of of which is water. The population density is .
Neighbouring municipalities are Alajärvi, Karstula, Kyyjärvi, Saarijärvi and ÃÂhtäri.
The municipality is unilingually Finnish.
The name is derived from the male name Soini, a Finnish variant of the Scandinavian name Sven. The village was first mentioned in 1754 as a part of the Alajärvi parish. Soini gained a chapel in 1784 and a church in 1859. It was fully separated from Alajärvi in 1895. Soini originally had a Swedish name, KonungsÃÂ¥by, which referred to the river Kuninkaanjoki.