State Route 345 (SR 345) is a north–south state highway in the eastern portion of the U.S. state of Ohio. The southern terminus of SR 345 is at a signalized intersection with the SR 13/SR 37 concurrency in New Lexington. Its northern terminus is at a T-intersection with U.S. Route 22 (US 22) in the unincorporated community of East Fultonham.