Williston Lake is a reservoir created by the W. A. C. Bennett Dam and is located in the Northern Interior of British Columbia, Canada. The lake fills the basin of the upper Peace River, backing into the Rocky Mountain Trench which is where the Parsnip and Finlay met at Finlay Forks to form the Peace. The lake includes three reaches, the Peace Reach (formerly the Peace Canyon), and the Parsnip and Finlay Reaches, which are the lowermost basins of those rivers, and covers a total area of 1,761 sq km (680 sq mi), being the largest lake in British Columbia and the seventh largest reservoir in the World.
The reservoir is fed by the Finlay, Omineca, Ingenika, Ospika, Parsnip, Manson, Nation and Nabesche Rivers and by Clearwater Creek, Carbon Creek, and other smaller creeks. Several provincial parks are maintained on the shore of the lake, including Muscovite Lakes Provincial Park, Butler Ridge Provincial Park, Heather-Dina Lakes Provincial Park and Ed Bird-Estella Provincial Park.