Not to be confused with Warren County, Ohio. Warren is a city in and the county seat of Trumbull County, Ohio, United States. The municipality is located in northeastern Ohio, approximately 14 miles (23 km) northwest of Youngstown and 15 miles (24 km) west of the Pennsylvania state line. The population was 41,557 at the 2010 census. Warren is part of the Youngstown-Warren-Boardman, OH-PA Metropolitan Statistical Area.