Mattagami River

The Mattagami River is a river in Northern Ontario, Canada.

The Mattagami flows 443 km from its source at Mattagami Lake in geographic Gouin Township in the Unorganized North Part of Sudbury District, on the Canadian Shield southwest of Timmins, to Portage Island in geographic Gardiner Township in the Unorganized North Part of Cochrane District, in the Hudson Bay Lowlands. Here the Mattagami's confluence with the Missinaibi River forms the Moose River, about 100 km from that river's tidewater outlet at James Bay. The Mattagami River flows through the city of Timmins as well as the town of Smooth Rock Falls and its drainage basin encompasses 37000 km2.

The Mattagami's name comes from the Ojibwe and means either "the start of water" (maadaagami) or "turbulent water" (madaagami), but the local Ojibwe population claim "Mattagami" is a corrupted form of "confluence" (maadawaagami). According to the Mattagami First Nation, Mattagami means "Meeting of the Waters".

Course
The river starts at Mattagami Lake and ends at its confluence with Missinaibi River, serving as a source for Moose River.

Economy
Where the Groundhog and Kapuskasing Rivers flow into the Mattagami, Ontario Power Generation operates the Little Long Generating Station, with a dam just over 5 km in length.

Tributaries
Tributaries include the:
 * Kapuskasing River
 * Nemegosenda River
 * Chapleau River
 * Groundhog River
 * Ivanhoe River
 * Nat River
 * Poplar Rapids River
 * Kamiskotia River
 * Grassy River
 * Tatachikapika River
 * Mattagami Lake
 * Minisinakwa River
 * Nabakwasi River
 * Opikinimika River
 * Noble River