Mammamattawa is a dispersed rural community and unincorporated place in the Unorganized North Part of Cochrane District in northeastern Ontario, Canada.

[3][6] The Constance Lake First Nation operates a camp at Mammamattawa.

[7] The first inland post of the Hudson's Bay Company, named Henley House, was established at the confluence of the Kenogami River and Albany River in 1743.

[11] The English River First Nation, the primary forerunner to today's Constance Lake First Nation, had a reserve set aside for their use just north of the post in 1912, which remains part of the Constance Lake First Nations lands as English River 66 Indian Reserve.

[3][6][11][12] The Hudson's Bay Company English River Post was abandoned in 1941, and the place later took on its present First Nations name.