Lake Winnipeg (French: Lac Winnipeg, Ojibwe: ᐑᓂᐸᑲᒥᐠᓴᑯ˙ᑯᐣ, romanized: Weenipagamiksaguygun) is a very large, relatively shallow 24,514-square-kilometre (9,465 sq mi) lake in North America, in the province of Manitoba, Canada. Its southern end is about 55 kilometres (34 mi) north of the city of Winnipeg. Lake Winnipeg is Canada's sixth-largest freshwater lake and the third-largest freshwater lake contained entirely within Canada, but it is relatively shallow (mean depth of 12 m [39 ft]) excluding a narrow 36 m (118 ft) deep channel between the northern and southern basins. It is the eleventh-largest freshwater lake on Earth. The lake's east side has pristine boreal forests and rivers that were in 2018 inscribed as Pimachiowin Aki, a UNESCO World Heritage Site. The lake is 416 km (258 mi) from north to south, with remote sandy beaches, large limestone cliffs, and many bat caves in some areas. Manitoba Hydro uses the lake as one of the largest reservoirs in the world. There are many islands, most of them undeveloped.

The Sagkeeng First Nation holds a reserve on Turtle Island, in the southern part of the lake. The Anishinaabe people have been in this area for thousands of years, long before European settlers.