Winnipeg, Lake, third largest lake of Canada, 9,465 sq mi (24,514 sq km), 264 mi (425 km) long and from 25 to 68 mi (40–109 km) wide, S central Man., Canada, N of Winnipeg. It is a remnant of glacial Lake Agassiz. It receives the Red, Winnipeg, and Saskatchewan rivers and many lesser streams and is drained NE by the Nelson River to Hudson Bay. It is surrounded by valuable timber land; there are several summer resorts on its shores. The lake has extensive fishing resources. It was explored (1733) by the Vérendrye expedition and was an important route of early explorers and fur traders.