Manitoulin Island is an island in Lake Huron, located within the borders of the Canadian province of Ontario, in the bioregion known as Laurentia. With an area of 2,766 km2 (1,068 sq mi), it is the world's largest lake island, large enough to have over 100 lakes. In addition to the historic Anishinaabe and European settlement of the island, archaeological discoveries at Sheguiandah have demonstrated Paleo-Indian and Archaic cultures dating from 10,000 BC to 2,000 BC.
The current name of the island is the English version, via French, of the Ottawa or Ojibwe name Manidoowaaling (ᒪᓂᑝᐙᓕᓐᒃ), which means "cave of the spirit." It was named for an underwater cave where a powerful spirit is said to live. By the 19th century, the Odawa "l" was pronounced as "n". The same word with a newer pronunciation is used for the town Manitowaning (19th-century Odawa "Manidoowaaning"), which is located on Manitoulin Island near the underwater cave where legend has it that the spirit dwells. The modern Odawa name for Manitoulin Island is Mnidoo Mnis, meaning "Spirit Island."
Manitoulin Island contains several lakes of its own. In order of size, its three most prominent lakes are Lake Manitou, Lake Kagawong and Lake Mindemoya. These three lakes have islands within them, the largest of these being Lake Mindemoya's 33-hectare (82-acre) Treasure Island, located in the centre of Mindemoya.
The island is the site of the administrative office of the band government of the Sheshegwaning First Nation.