Bandak is a lake in the municipalities of Kviteseid and Tokke in Telemark county, Norway. The lake, which is part of the Telemark Canal route, belongs to the Skien watershed. The river Tokke flows into the lake, and the outlet is via the river Strauman, which flows to the lake Kviteseidvatn. The lake has an area of 26.8 km2. The average depth of the lake is 121 m which is about 49 m below sea level. The deepest part of the lake reaches 325 m which makes it the eighth deepest lake in Norway. The 27 km long lake measures about 2 km at the widest. The catchment area for the lake is about 2545.7 km2. The Tokke Hydroelectric Power Station utilizes the hydraulic head from the nearby lake Vinjevatn to Bandak of about 394 m to generate electricity. It is one of northern Europe's largest power plants with a production of some 430 MW. The plant produces an average annual production of 2140 GWh.