State Route 13 is a north–south state highway in the northern and southeastern portion of the U.S. state of Ohio. It is the tenth longest state route in Ohio. Its southern terminus is at State Route 550 near Athens, and its northern terminus is at U.S. Route 6 in Huron.

State Route 550 is an east–west state highway in the southeastern portion of the U.S. state of Ohio. The western terminus of SR 550 is at an interchange with U.S. Route 33 (US 33) just north of the city limits of Athens, immediately south of the southern terminus of SR 13. The eastern terminus of SR 550 is at an intersection with SR 7 just west of Marietta.