Wahwashkesh Lake is a lake in Whitestone, Parry Sound District, Ontario, Canada, and is the largest lake in Parry Sound District, with a surface area of 4,253 acres and over 106 km of shoreline. Approximately 30% of the shoreline property is Crown Land. The lake has two distinct basins – Top Lake is the smaller of the two, and the Big Lake. Wahwashkesh is part of the Magnetawan River system, and the lake is renowned for an extremely severe spring freshet with the lake levels often rising 3 to 4 meters above the concrete weir at the outlet of the river.

The lake has a diverse fishery with over 12 species of sport fish, including Northern Pike, Walleye, Smallmouth, and Largemouth Bass. The lake ranks in the top five of all lakes in Ontario for such flora, which the Natural Heritage League and the World Wildlife Fund documented extensively in a 1989 study.