St. Clairsville
- County:
- Belmont County
- County Seat:
- Yes
- Area (mi²):
- 2.422
- State:
- Ohio
St. Clairsville is a city located in Belmont County, Ohio. St. Clairsville has a 2026 population of 4,954. It is also the county seat of Belmont County. St. Clairsville is currently declining at a rate of -0.42% annually and its population has decreased by -2.36% since the most recent census, which recorded a population of 5,074 in 2020.