State Route 172 is an east–west state highway in the northeastern portion of the U.S. state of Ohio. Its western terminus is at its interchange with U.S. Route 30 about 1-mile (1.6 km) west of East Greenville near Dalton, and its eastern terminus is at U.S. Route 30 about 2 miles (3.2 km) west of Lisbon. The route stays near the U.S. Route 30 for its entire route, and some of the current Route 172 actually served as previous alignments of U.S. 30.