Manitoulin Island is a Canadian lake island in Lake Huron, in the province of Ontario. It is the largest freshwater lake island in the world. Manitoulin Island contains a number of lakes of its own. In order of size, its three most prominent lakes are Lake Manitou, Lake Kagawong and Lake Mindemoya. Each of these three lakes in turn have islands within them, the largest of these being Lake Mindemoya's 82-acre Treasure Island, located in the centre of Manitoulin.
The island is the site of the administrative office of the Sheshegwaning First Nations band government.