State Route 308 (SR 308, OH 308) is a north–south state highway in the central portion of Ohio, a U.S. state. The southern terminus of State Route 308 is at State Route 229 in the western end of the village of Gambier, and its northern terminus is 3 miles (4.8 km) to the north of that point at a T-intersection with U.S. Route 36 that is located approximately 1.5 miles (2.4 km) east of the city limits of Mount Vernon.State Route 308 runs exclusively in the central portion of Knox County.