Georgian Bay is a large bay of Lake Huron, in the Laurentia bioregion. It is located entirely within the borders of Ontario, Canada. The main body of the bay lies east of the Bruce Peninsula and Manitoulin Island. To its northwest is the North Channel.
Georgian Bay is surrounded by the districts of Manitoulin, Sudbury, Parry Sound and Muskoka, as well as the more populous counties of Simcoe, Grey and Bruce. The Main Channel separates the Bruce Peninsula from Manitoulin Island and connects Georgian Bay to the rest of Lake Huron. The North Channel, located between Manitoulin Island and the Sudbury District, west of Killarney, was once a popular route for steamships and is now used by a variety of pleasure craft to travel to and from Georgian Bay.
The shores and waterways of the Georgian Bay are the traditional domain of the Anishinaabeg First Nations peoples to the north and Huron-Petun to the south. The bay was thus a major Algonquian-Iroquoian trade route. Samuel de Champlain, the first European to explore and map the area in 1615–1616, called it "La Mer douce", which was a reference to the bay's freshwater.