Square Lake is a lake in Washington County, in the U.S. state of Minnesota. Located near Stillwater, Minnesota it is a popular destination for fishing, swimming, and Scuba diving. The lake has a surface area of approximately 203 acres and a maximum depth of 68 feet. The Minnesota Department of Natural Resources lists fish species present in Square Lake as: Northern Pike, Largemouth Bass, Bluegill, Crappie, Rainbow Trout, Bullhead species, and Yellow Perch.