Aurora is a home rule city located in Arapahoe, Adams, and Douglas counties, Colorado, United States. The city's population was 386,261 at the 2020 census, with 336,035 in Arapahoe County, 47,720 in Adams County, and 2,506 in Douglas County. It is the third-most-populous city in the state of Colorado and the 50th-most-populous city in the United States as of 2025. Aurora is a principal city of the Denver–Aurora–Centennial, CO Metropolitan Statistical Area and the Denver-Aurora-Greeley, CO Combined Statistical Area, and a major city of the Front Range Urban Corridor.