Lake Mistassini (in French: Lac Mistassini) is the largest natural lake by surface area in the province of Quebec, Canada, with a total surface area of approximately 2,335 km² and a net area (water surface area only) of 2,164 km². It is located in the Jamésie region of the province, approximately 360 kilometers (220 mi) east of James Bay. The Cree town of Mistissini is located on Watson Peninsula in the south-east corner of the lake, which separates Baie du Poste from Abatagouche Bay.