State Route 188 (SR 188) is a 39.04-mile-long (62.83 km) east–west state highway located in the central part of the U.S. state of Ohio. SR 188's western terminus is in Circleville at a signalized intersection where it meets the concurrency of U.S. Route 22 (US 22) and SR 56. Its eastern terminus is at a signalized intersection with SR 204 in the central business district of the village of Thornville.