Gråsjøen is a lake/reservoir in the municipality of Surnadal (and a very small part in the northeastern corner of the lake is in Rindal) in Møre og Romsdal county, Norway. The lake is located in the northern part of the Trollheimen mountain range. The lake is dammed and the water is used in the Gråsjø power station. The water flows out of the lake and into the lake Foldsjøen.