Gagnåsvatnet or Gangåsvatnet is a lake in the municipality of Orkland in Trøndelag county, Norway. The 5.49-square-kilometre (1,360-acre) lake is located about 9 kilometres (5.6 mi) southwest of the town of Orkanger and about 6 kilometres (3.7 mi) west of the village of Fannrem in the Orkdalen valley.

The water flows into the lake from the Songa river which flows out of the lake Våvatnet which is also in Orkland. The water leaves the lake through the Skjenaldelva river which ultimately flows into the Trondheimsfjord. The lake Hostovatnet lies about 7 kilometres (4.3 mi) south of the lake.

• List of lakes in Norway