Sunday Lake is an unorganized territory located in Saint Louis County, Minnesota, United States. As of the 2000 census, its population was zero.
According to the United States Census Bureau, the unorganized territory has a total area of 26.5 square miles (68.7 km2); 21.5 square miles (55.6 km2) is land and 5.1 square miles (13.2 km2) is water. The total area is 19.19% water.