Jefferson County is a county located in the U.S. state of Ohio. As of the 2020 census, the population was 65,249. Its county seat is Steubenville. The county is named for Thomas Jefferson, who was vice president at the time of its creation.

Steubenville is a city in and the county seat of Jefferson County, Ohio, United States. Located along the Ohio River 33 miles (53 km) west of Pittsburgh, it had a population of 18,161 at the 2020 census. The city's name is derived from Fort Steuben, a 1786 fort that sat within the city's current limits and was named for Prussian military officer Baron Friedrich Wilhelm von Steuben. It is a principal city of the Weirton–Steubenville metropolitan area, which had a 2020 population of 116,903 residents.