Hainesville is an unincorporated community in north-central Hampshire County, West Virginia, United States. It is situated at the crossroads of Old Martinsburg Grade Road (County Route 45/9), Little Cacapon Mountain Road (County Route 45/10), and Voits Road (County Route 45/11), to the southwest of Slanesville.
The U.S. Post Office Department established a post office at Hainesville on February 11, 1878, with James Haines serving as its first postmaster. The post office was disestablished on April 9, 1895, and Hainesville's mail was then routed to the Barnes Mill post office. Hainesville was alternatively known as Haines Store.