Beallsville is a village in Monroe County, Ohio, United States. As of the 2020 census, the population was 355. The village gained national attention by losing more than 1% of its population killed in action in the Vietnam War, the worst per-capita loss of life experienced by any place in the country.

Monroe County is a county located on the eastern border of the U.S. state of Ohio, across the Ohio River from West Virginia. As of the 2020 census, the population was 13,385, making it the second-least populous county in Ohio. Its county seat is Woodsfield. The county was created in 1813 and later organized in 1815.