The Missinaibi River is a river in northern Ontario, Canada, which flows northeast from Missinaibi Lake north of Chapleau , Ontario and empties into the Moose River, which empties into James Bay. This river is approximately 713 km in length.

In the days of the fur trade, this river provided access to James Bay by way of the Moose River and to Lake Superior by way of the Michipicoten River. There is also evidence that native peoples used the river as a trading route long before that time. This route was used by traders from both the Hudson's Bay Company and the North West Company. A number of trading posts were built along the river in the late 18th century and the fur trade continued until the late 19th century. Today, the river is used for canoeing, fishing and camping. It is managed as a provincial waterway park and has been nominated as a Canadian Heritage River.

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.

Tributaries include the:

• Brunswick River
• Fire River
• Hay River
• Mattawitchewan River
• Pivabiska River
• Opasatika River
• Soweska River

See also

• List of Ontario rivers
• James Bay Rivers