Willow Lake is a census-designated place (CDP) surrounding a lake of the same name in Stephenson County, Illinois, United States.

It is in the center of the county, on the north side of U.S. Route 20 and 3 miles (5 km) north of the center of Freeport, the county seat.

Willow Lake was first listed as a CDP prior to the 2020 census.

Willow Lake first appeared as a census designated place in the 2020 U.S.

This Stephenson County, Illinois location article is a stub.