Rainy Lake is a freshwater lake with a surface area of 360 square miles (932 km2) that straddles the border between the United States and Canada. The Rainy River issues from the west side of the lake. Today it is harnessed to make hydroelectricity for US and Canadian locations. International Falls, Minnesota and the much smaller city of Ranier, Minnesota are situated opposite Fort Frances, Ontario, on either side of the Rainy River. Rainy Lake and Rainy River establish part of the boundary between the US state of Minnesota and the Canadian province of Ontario.

The Rainy River is a river, approximately 137 miles (220 km) long, forming part of the Canada–United States border separating Northwestern Ontario and northern Minnesota.