Highlands Ranch is an unincorporated community and a census-designated place (CDP) located in and governed by Douglas County, Colorado, United States. The CDP is a part of the Denver–Aurora–Lakewood, CO Metropolitan Statistical Area. The population of the Highlands Ranch CDP was 105,631 at the 2020 census, making it the most populous unincorporated community in the State of Colorado. The Highlands Ranch Metropolitan District provides services to the community, which lies in ZIP Codes 80126, 80129, 80130, and 80163.

Douglas County is a county located in the U.S. state of Colorado. As of the 2020 Census, the population was 357,978. The county is named in honor of U.S. Senator Stephen A. Douglas. The county seat is Castle Rock.