Lone Tree is a home rule municipality located in northern Douglas County, Colorado, United States. The population was 14,253 at the 2020 census, and was estimated to be 14,061 in 2024. Austrian immigrant brothers John, Joseph, and Jacob Schweiger established a homestead in 1874 that would become Schweiger Ranch, among the area's earliest European settlements.
The modern city traces its origins to Memorial Day weekend 1982, when a new residential subdivision opened with nine households. Residents organized as the Lone Tree Homeowners Association and, lacking local governance as part of unincorporated Douglas County, grew increasingly frustrated with issues including unenforced zoning standards and absent infrastructure. By 1991 the area had grown to encompass 13 homeowners' associations but still lacked formal municipal authority.
The city's high design standards shaped its early development. When IKEA sought to build a location in Lone Tree, the city declined due to the company's signature blue and yellow exterior not meeting local standards; IKEA subsequently built in neighboring Centennial.
The city's terrain transitions from developed suburban areas in the north and west to the elevated grassland bluffs of Bluffs Regional Park in the south, which offer panoramic views of the Front Range from Longs Peak to Pikes Peak.
The city annexed the territory of the University of Colorado South Denver campus, the former site of The Wildlife Experience, in 2017. Following the university's closure in 2021, the Douglas County School District purchased the 14.1-acre property for $10.3 million and converted it into the Legacy Campus, a Career and Technical Education facility that opened in August 2023.