Aurora (, ) is a home rule municipality 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 residing in Arapahoe County, 47,720 residing in Adams County, and 2,506 residing in Douglas County. Aurora is the third-most-populous city in the State of Colorado and the 52nd-most-populous city in the United States. Aurora is a principal city of the Denver–Aurora–Lakewood Metropolitan Statistical Area (MSA) and a major city of the Front Range Urban Corridor.