Long Lake is an unincorporated community and census-designated place (CDP) in Lake County, Illinois, United States. Per the 2020 census, the population was 3,663.
Geography
The community is in western Lake County and nearly surrounds Long Lake, which drains northwest via Manitou Creek to Fox Lake, part of the Chain O'Lakes of northern Illinois. The CDP is bordered to the northeast by the village of Round Lake Heights and to the east and south by the village of Round Lake Beach. The CDP is primarily in the eastern part of Grant Township, with a smaller portion in the northwest corner of Avon Township, and an area of about one city block in the southwest corner of Lake Villa Township.
Illinois Route 134 runs along the southern edge of the CDP, leading west to U.S. Route 12 in the southern part of Fox Lake and southeast through Round Lake Beach to Hainesville. Long Lake is northwest of downtown Chicago.
According to the 2021 census gazetteer files, Long Lake has a total area of , of which (or 66.29%) is land and (or 33.71%) is water.