Storsjön (, lit. "The Great Lake") is the fifth largest lake in Sweden, with an area of 464 km² and a greatest depth of 74 m. It is located in the province of Jämtland in modern Jämtland County. From Storsjön runs the river Indalsälven and the lake contains the major island Frösön. The city of Östersund is located on the east shore of the lake, opposite Frösön.