Cairo is a town in Ritchie County, West Virginia, United States, along West Virginia Route 31, the North Fork of the Hughes River, and the North Bend Rail Trail. The population was 174 at the 2020 census.

Ritchie County is a county in the U.S. state of West Virginia. As of the 2020 census, the population was 8,444. Its county seat is Harrisville. The county was created in 1843 by the Virginia General Assembly and named for Richmond newspaper publisher Thomas Ritchie.