The Rupert River is one of the largest rivers in Quebec. Its headwaters are in lake Mistassini, from which it flows west into James Bay. There is some extremely large whitewater on the river, but as a paddler much can be avoided by sneak routes on the side. The most impressive falls (which cannot be avoided except by portaging...) are The Fours near the end of the river.

The Rupert has long been an important river for the Cree of the area. Every year, a group of Cree youth from the town of Waskaganish, Quebec (at the mouth of the Rupert) travel up the river to Lac Nemiscau.

The Rupert is presently threatened by hydroelectric development (see James Bay). HydroQuebec has begun building a series of dams and canals which will divert about 90% of the Rupert's water north into the Eastmain reservoir where it will contribute to the massive amount of power generation there.