State Route 518 (SR 518) is an east–west state highway located entirely in Columbiana County in northeast Ohio. The western terminus of State Route 518 is at State Route 644 approximately 2 miles (3.2 km) north of Summitville. Its eastern terminus is at the duplex of U.S. Route 30 and State Route 45 near West Point.

Originally created in the late 1930s, State Route 518 runs through rural portions of Columbiana County. passing through scattered small, unincorporated communities along the way.

State Route 518 was designated in 1937 along the routing that it currently occupies. Ths highway has not experienced any major changes since its inception.

The entire route is in Columbiana County.