Arstaddalsdammen is a lake that lies in Beiarn Municipality in Nordland county, Norway. It is located about 15 kilometres (9.3 mi) southwest of the village of Moldjord. The 2.54-square-kilometre (0.98 sq mi) lake lies in the southern end of the Arstaddal valley, and it has a dam on the northern end. The dam was built in the 1960s. The water from the lake is piped to the nearby lake Sokumvatnet in Gildeskål Municipality. The lake serves as a reservoir for the Sundsfjord Hydroelectric Power Station.