Sperillen is a lake in the valley of Ådal in Ringerike municipality, Buskerud county, Norway. The lake has an area of 37 km² and extending about 26 km in length. It is 108 meters deep at its deepest and lies at 150 meters above sea level. Two rivers from Oppland, Begna from the valley of Begnadalen and Urula from the valley of Hedalen, flow into the lake at the northern end on either side of the town of Nes in Ådal. At the southern end, Ådal river flows downstream from Sperillen. The outflow powers a hydro-electric power station at Ringmoen. European route E16 follows the east side of the lake.