Lake Crystal is a city in Blue Earth County, Minnesota, United States, established in 1869. The population was 2,539 at the 2020 census. It is part of the Mankato-North Mankato Metropolitan Statistical Area.

Blue Earth County is a county in the State of Minnesota. As of the 2020 census, the population was 69,112. Its county seat is Mankato. The county is named for the Blue Earth River and for the deposits of blue-green clay once evident along the banks of the Blue Earth River. Blue Earth County is part of the Mankato-North Mankato metropolitan area.