Gap Mills is an unincorporated community in Monroe County, West Virginia, United States. Established in 1775 and located on West Virginia Route 3 east of Union, Gap Mills has a post office with ZIP code 24941. Fort Henry commander Abraham Wood sent the first recorded English expedition to reach the area in 1671. The name of the community is a portmanteau of the natural pass, or "gap" in the adjacent Gap Mountain and two grist mills that were once located there.