Lake Manitou is the largest lake

Lake

A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

 on Manitoulin Island

Manitoulin Island

Manitoulin Island is a Canadian island in Lake Huron, in the province of Ontario. It is the largest island in a freshwater lake in the world. In addition to the historic Anishinaabe and European settlement of the island, archeological discoveries at Sheguiandah have demonstrated Paleo-Indian and...

 in Ontario

Ontario

Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....

, Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

. It is the largest lake on a freshwater island in the world. Since Manitoulin Island itself is in Lake Huron

Lake Huron

Lake Huron is one of the five Great Lakes of North America. Hydrologically, it comprises the larger portion of Lake Michigan-Huron. It is bounded on the east by the Canadian province of Ontario and on the west by the state of Michigan in the United States...

, one of the Great Lakes

Great Lakes

The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...

, Manitou qualifies as the largest "lake in a lake". Lake Manitou has an area of about 104 square kilometres (40.2 sq mi). It is drained by the Manitou River

Manitou River (Manitoulin Island)

The Manitou River is a river in Ontario, Canada. It is approximately 15 km in length.It starts at the south end of Lake Manitou at a dam in Sandfield, ON in the Township of Central Manitoulin and ends at Michael's Bay on Lake Huron at the south end of Manitoulin Island.The Blue Jay Creek and...

. There are also a number of small islands in Lake Manitou, making them islands in a lake on an island in another lake.