Big Spirit Lake is a natural body of water, approximately 5,684 acres (2,300 ha) in area, in Dickinson County in northwest Iowa in the United States. It is part of the chain of lakes known as the Iowa Great Lakes, the northern shore of the lake straddles the border with Minnesota. It is the largest natural lake in Iowa. The Dakotah Indian name for the lake was Minnewaukon. Early French traders named it Lac D' Esprit after the Indian legends of an evil spirit who dwelled in the lake.
Its maximum depth is 24 feet (7.3 m), and the mean depth is 17 feet (5 m). The drainage area of the lake is approximately 22 square miles (57 km²). It has a drainage area of approximately 75 mi² (194 km²), most of which is in Minnesota.