State Route 198 is a north–south state highway in the western portion of the U.S. state of Ohio. Its southern terminus is at an interchange with U.S. Route 33 just south of Wapakoneta, which is also the western terminus of State Route 67 and the southern terminus of State Route 501; its northern terminus is at State Route 117 nearly 4 miles (6.4 km) east of Spencerville.