Warren is a city in Trumbull County, Ohio, United States, and its county seat. The population was 39,201 at the 2020 census. Located along the Mahoning River, Warren lies approximately 14 miles (23 km) northwest of Youngstown and 56 miles (90 km) southeast of Cleveland. It was the historical county seat of the Connecticut Western Reserve and is a principal city of the Mahoning Valley metropolitan area in Northeast Ohio.