is a city in the U.S. state of Ohio and the county seat of Trumbull County. The municipality is located in northeastern Ohio, approximately 14 miles (22 km) northwest of Youngstown and 15 miles (24 km) west of the Pennsylvania state line.
The population was 46,832 at the 2000 census, but in 2005, the population was down to 45,796. It is part of the Youngstown-Warren-Boardman, OH-PA Metropolitan Statistical Area.
Ephraim Quinby founded Warren in 1798, on 441 acres of land that he purchased from the Connecticut Land Company, as part of the Connecticut Western Reserve. Quinby named the town for the town's surveyor, Moses Warren. The town became the Trumbull County seat in 1801.
The first 'flag cancel' machine was invented and installed in 1899 at the Warren Post Office.