West Virginia Route 31 is a north–south state highway in the northwestern portion of the U.S. state of West Virginia. The northern terminus of the main portion of the route is at West Virginia Route 14 near Interstate 77 Exit 185 southeast of Williamstown. The southern terminus is at West Virginia Route 16 in Harrisville.

West Virginia Route 31 is also the designation given to the unsigned highway connecting West Virginia Route 14 in Williamstown to the Williamstown Bridge over the Ohio River.