Langsjøen is a lake in the municipalities of Tolga and Engerdal in Innlandet county, Norway. The 6.35-square-kilometre (2.45 sq mi) lake lies in the Sømådalen valley in the southeastern part of the municipality, just west of the large lake Femund. The village of Øversjødalen lies at the north end of the lake and the mountain Elgspiggen lies about 10 kilometres (6.2 mi) west of the lake.[1]