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 United States census with 336,035 living in Arapahoe County, 47,720 in Adams County, and 2,506 in Douglas County. Aurora is the third-most-populous city in the State of Colorado and the 51st-most-populous city in the United States. Aurora is a principal city of the Denver–Aurora–Centennial, CO Metropolitan Statistical Area and the Denver-Aurora, CO Combined Statistical Area, and a major city of the Front Range Urban Corridor.