Gilmer County is a county in the U.S. state of West Virginia. As of the 2020 census, the population was 7,408, making it West Virginia's fifth-least populous county. Its county seat is Glenville. The county was formed in 1845 from parts of Lewis and Kanawha Counties, and named for Thomas Walker Gilmer, Governor of Virginia from 1840 to 1841. Gilmer was later a representative in the United States Congress and Secretary of the Navy in President John Tyler's cabinet.