West Union is a village in Adams County, Ohio, United States, about 55 miles (89 km) southeast of Cincinnati. The population was 3,004 at the 2020 census. It is the county seat of Adams County. West Union is served by West Union High School, the Adams County/Ohio Valley School District, and the West Union Public Library, a branch of the Adams County Public Library.

Adams County is a county in the U.S. state of Ohio. As of the 2020 census, the population was 27,477. Its county seat and largest village is West Union. The county is named after John Adams, the second President of the United States.