The Union of Ontario Indians is a First Nations political organization representing 39 member First Nations in the province of Ontario, Canada. The organization's roots predate European contact in the 16th century. It was incorporated in 1949 to serve as a political advocate and secretariat for the Anishinabek Nation, members of tribes speaking Anishinaabe languages. The head office for the Union of Ontario Indians is located at Nipissing First Nation near North Bay, Ontario.
The Union of Ontario Indians is guided by a Leadership Council, consisting of a Grand Council Chief, a Deputy Grand Council Chief and grand chief, and council members and elders representing four geographic regions: Southeast, Southwest, Lake Huron and Northern Superior.
In the early 21st century, there are about 60,000 citizens of the Anishinabek Nation member communities, accounting for about one-third of the total First Nations population in the province of Ontario.