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 north of the center of Freeport, the county seat. As of the 2020 census, Willow Lake had a population of 1,026.
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. census.
It is in the Freeport School District 145. The district operates Freeport High School.