Warren is a city in and the county seat of Warren County, Pennsylvania, United States, located along the Allegheny River. The population was 9,404 at the 2020 census. It is home to the headquarters of the Allegheny National Forest and the Cornplanter State Forest. It is also the headquarters for the Chief Cornplanter Council, the oldest continuously chartered Boy Scouts of America Council, and the catalog company Blair. Warren is the principal city of the Warren micropolitan area.