State Route 189 (SR 189, OH 189) is a 11.58-mile (18.64 km) long state highway in the northwestern portion of the U.S. state of Ohio. The highway runs from its western terminus at its junction with U.S. Route 224 (US 224) and SR 66 in Ottoville to its eastern terminus at the intersection of SR 115 and SR 12 in Vaughnsville, nearly 5 miles (8.0 km) southwest of Columbus Grove.