State Route 644 (SR 644) is a north–south state highway running through Columbiana and Carroll counties in northeast Ohio. Its southern terminus is at State Route 39 in downtown Salineville, and its northern terminus is at its junction with U.S. Route 30 and State Route 9 in the center of Kensington. The route connects mainly rural and a few unincorporated parts of southeastern Columbiana County.