(in Sami language Dåtnejaevrie
) is a lake
municipalities in Nord-Trøndelag
. It is 100.18 km² in area. It is 358 m above sea level with a depth of 220 m and a volume of 8.68 km³. It is one of the largest lakes
The island Gudfjelløya (Sami Tjåehkere) lies in Tunnsjøen lake. It has a high point of 812 m above sea level, which is 454 m higher than the lake. This makes Gudfjelløya the highest island on a lake in Norway.