Big Spirit Lake is a natural body of water, approximately 5,684 acres (23.01 km²) 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.