Clairton is a city in Allegheny County, Pennsylvania, United States. It is located along the Monongahela River and is part of the Pittsburgh metropolitan area. The population was 6,181 at the 2020 census. Under Pennsylvania legal classifications for local governments, Clairton is considered a third-class city. It is home to Clairton Works operated by U.S. Steel, the largest coke manufacturing facility in the United States.