It comprises Manitoulin Island and a number of small islands around it, making it the smallest district in Ontario. Previously it included the municipality of Killarney on the mainland, until this was transferred to Sudbury District in the late 1990s. Subsequently, more mainland portions were added to Killarney and these, together with Unorganized Mainland Manitoulin District, were also transferred to Sudbury District in 2006, about 1,600 square kilometres (600 sq mi) in all.
Like the other districts of Northern Ontario, the Manitoulin District does not have a county or regional municipality tier of government. All services in the district are provided either by the individual municipalities or directly by the provincial government. Services are provided jointly with the Sudbury District from its district seat in Espanola.
Manitoulin District is served by only one primary provincial highway, Highway 6. This highway enters the district at the ferry docks in South Baymouth, in the township of Tehkummah, where the Chi-Cheemaun ferry travels to and from Tobermory in the municipality of Northern Bruce Peninsula. It exits the district in the Whitefish River First Nation, just south of Whitefish Falls, when it crosses into the Sudbury District.
A number of secondary provincial highways, the equivalent in a district to a county or municipal road in Southern Ontario, serve the communities of Manitoulin Island. These are: