The Rupert River is one of the largest rivers in Quebec, Canada. From its headwaters in Lake Mistassini, the largest natural lake in Quebec, it flows west into Rupert Bay on James Bay. The Rupert drains an area of . There is some extremely large whitewater on the river, but paddlers can avoid much of it by portage routes on the side. The most impressive falls, which cannot be avoided except by portaging, are the "Oatmeal Rapids" right at the James Bay Road (a set of cascades dropping ) and "The Fours" near the end of the river (a drop).