The City of Castle Pines is a home rule municipality located in Douglas County, Colorado, United States. The city population was 11,036 at the 2020 United States Census. Castle Pines is a part of the Denver–Aurora–Lakewood, CO Metropolitan Statistical Area and the Front Range Urban Corridor. The city is located north of the Town of Castle Rock and south of the City of Lone Tree, Colorado.

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.