Big Hawk Lake is a lake in the Trent River and Lake Ontario drainage basins in Algonquin Highlands, Haliburton County, Ontario, Canada.The lake is about 4.7 kilometres (2.9 mi) long and 3.7 kilometres (2.3 mi) wide and lies at an elevation of 355 metres (1,165 ft) about 3 kilometres (1.9 mi) northeast of Ontario Highway 35. The primary inflow is the Kennisis River arriving from Nunikani Lake over Nunikani Dam at the north, and a channel from Little Hawk Lake at the south.