Lake Nipissing (French: lac Nipissing) is a lake in the Canadian province of Ontario. It has a surface area of 873.3 square kilometres (337.2 sq mi), a mean elevation of 196 metres (643 ft) above sea level, and is located between the Ottawa River and Georgian Bay. Excluding the Great Lakes, Lake Nipissing is the third-largest lake in Ontario. It is relatively shallow for a large lake, with an average depth of only 4.5 m (15 ft). The shallowness of the lake makes for many sandbars along the lake's irregular coastline.