Funnsjøen is a lake in the municipality of Meråker in Trøndelag county, Norway. The 8 km2 lake flows into the Funna river, a part of the Stjørdalselva river system. The lake has a hydropower dam at the southern end of the lake. There is about 64,000,000 m3 of water stored behind the dame in the lake. The lake is located about 6.5 km north of the municipal center of Midtbygda. The lake Feren lies north of the lake and the lake Fjergen lies southeast of the lake.