Gallia County is a county located in the U.S. state of Ohio. As of the 2020 census, the population was 29,220. Its county seat and largest village is Gallipolis.

Gallipolis is a chartered village in and the county seat of Gallia County, Ohio, United States. The municipality is located in Southeast Ohio along the Ohio River about 55 miles (89 km) southeast of Chillicothe and 44 miles (71 km) northwest of Charleston, West Virginia. The population was 3,313 at the 2020 census. Gallipolis is the second-largest community in the rural Point Pleasant micropolitan area, which includes all of Gallia County, Ohio, and Mason County, West Virginia.