Farris is a lake on the border of Telemark and Vestfold counties in Norway. The 20 km long freshwater moraine-dammed lake is located mostly in Larvik Municipality in Vestfold, but the northwestern part of the lake is located in Siljan Municipality and Porsgrunn Municipality in Telemark. The large town of Larvik is located at the southern end of the lake. The 21 km2 lake would have been part of the saltwater Larviksfjorden, had it not been dammed by an end moraine left by the latest ice age. That moraine is about 1 km wide, separating the lake from the sea. There is a short river that runs through the moraine which drains the lake into the fjord. The lake Farris is a drinking water reservoir for about 170,000 people in the region. The largest island in the lake is Bjørnøya, located just east of the village of Kjose. The mineral water brand Farris is named after the lake.