Warrenton is a town in Fauquier County, Virginia, United States. It is the county seat. The population was 10,057 as of the 2020 census, an increase from 9,611 at the 2010 census and 6,670 at the 2000 census. The estimated population in July 2021 was 10,109. It is at the junction of U.S. Route 15, U.S. Route 17, U.S. Route 29, and U.S. Route 211. The town is in the Piedmont region of Virginia just east of the Blue Ridge Mountains.