Helgøya is an island in the lake Mjøsa. The 18.3-square-kilometre (7.1 sq mi) island is located in Ringsaker Municipality in Innlandet county, Norway. The island is the largest freshwater island in Norway. The island is located south of the Nes peninsula, and it has been connected to the mainland by the since 1957. The island was formerly a part of the Nes Municipality until 1964.