State Route 172 (SR 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 (US 30) about one mile (1.6 km) west of East Greenville near Dalton, and its eastern terminus is at US 30 about two miles (3.2 km) west of Lisbon. The route stays near US 30 for its entire route, and some of the current Route 172 actually served as previous alignments of US 30.

U.S. Route 30 (US 30) is a United States Numbered Highway that runs from Astoria, Oregon, to Atlantic City, New Jersey. In the state of Ohio, it is a major, 245-mile-long (394 km), east–west highway that runs through the northern section of the state. Overall, the highway runs through rural areas dominated by farm fields or woodlands; some segments are urban in character in the Mansfield and Canton areas.