Helgøya is an island in Mjøsa located in the Ringsaker municipality of Innlandet county, Norway. It was formerly a part of the Nes municipality.With an area of 18.3 km², Helgøya is the largest fresh-water island in Norway. The island is located south of the Nes peninsula, and has been connected to the mainland by the Nessundet Bridge since 1957.