Lake Nipigon (French : lac Nipigon) is the largest lake entirely within the boundaries of the Canadian province of Ontario and is sometimes described as the sixth Great Lake. Lying 260 m (853 ft) above sea level, the lake drains into the Nipigon River and thence into Nipigon Bay of Lake Superior. The lake and river are the largest tributaries of Lake Superior. It lies about 120 km (75 mi) northeast of the city of Thunder Bay, Ontario.