Oulujärvi (pronunciation. ^*) is the fifth largest lake in Finland, at 930 km². It is located in the north-central region of the country and is drained by the Oulu River, which flows northwestward from the lake to the Gulf of Bothnia. Its nickname is the "Kainuu sea", as it is surrounded by Kainuu municipalities.

About 40 percent of the lake is in the Vaala municipality.

Lakes of Finland

Oulujärvi | Oulusee | Oulujärvi | Oulujärvi | Jezioro Oulu | Оулуярви | Oulujärvi | Ule träsk