Missinaibi Provincial Park

Missinaibi River
Thunderhouse Falls
Country	Canada
Province	Ontario
Region	Algoma District, Cochrane District
Source	Missinaibi Lake
- location	12 km SSW from Peterbell inside the Chapleau Crown Game Preserve, Algoma District
- coordinates	48°29′56″N 83°25′52″W / 48.49889°N 83.43111°W / 48.49889; -83.43111
Mouth	Moose River
- location	Unorg. Cochrane District
- coordinates	50°44′08″N 81°28′02″W / 50.73556°N 81.46722°W / 50.73556; -81.46722Coordinates: 50°44′08″N 81°28′02″W / 50.73556°N 81.46722°W / 50.73556; -81.46722
Length	426 km (265 mi)
Basin	23,500 km2 (9,100 sq mi)

The Missinaibi River is a river in northern Ontario, Canada, which flows northeast from Missinaibi Lake, north of Chapleau, and empties into the Moose River, which drains into James Bay. This river (including Missinaibi Lake and Moose River to James Bay) is 755 kilometres (469 mi) in length. It is one of the longest free-flowing and undeveloped rivers in Ontario.

The river's name means "pictured waters" in the Cree language which is thought to refer to the pictographs found on rock faces along the river.

At Thunderhouse Falls, which is actually a chain of relatively small waterfalls connected by violent rapids, the river drops 40 metres, part of its descent from the Canadian Shield to the Hudson Bay Lowlands.

In fur trade days the Missinaibi was the main route between James Bay and Lake Superior. The route was: James Bay, Moose Factory, Moose River (Ontario), Missinaibi River, Missinaibi Lake, portage probably via Crooked Lake, Dog Lake, Michipicoten River to Fort Michipicoten on Lake Superior. Trade was contested by the English from the north and the French from the south. In 1774 the Hudson's Bay Company began building posts in the interior. In 1775-76 Edward Jarvis from Henley House went up the Kenogami River, crossed to the Missinaibi and went down to Michicopicten. In 1781 Philip Turnor surveyed the Missinaibi route to Michicopicten.