Algoma—Manitoulin is a long-standing provincial electoral district in Ontario, Canada, represented in the Legislative Assembly since 1934.

Between 1986 and 1999, the riding included nearly all of Algoma District, with the exception of two townships south of Hearst, as well as areas in the southeast such as Elliot Lake, everything east of it, and the City of Sault Ste. Marie.

In 1996, Ontario adopted the same electoral boundaries used at the federal level. This meant districts were redistributed whenever a federal boundary readjustment occurred.

In 2005, new legislation expanded Ontario to 107 provincial electoral districts, effective in the 2007 election. For Northern Ontario, eleven ridings—including Algoma—Manitoulin—remained consistent with the federal boundaries established in 1996 (with only minor adjustments). The southern 96 ridings were based on the 2003 federal boundaries drawn from the 2001 census. Without this legislation, Northern Ontario would have lost representation, with its number of ridings reduced from eleven to ten.
Today, Algoma—Manitoulin continues to serve as a vital electoral district, representing the diverse communities of Northern Ontario and ensuring their voice is heard in provincial governance.