State Route 73 is an east–west state highway in the southern portion of the U.S. state of Ohio. Its western terminus is on U.S. Route 27 in Oxford. State Route 73’s eastern terminus is in Portsmouth at U.S. Route 23; this is also the southern terminus of State Route 104, and the two state routes run concurrent for over 6 miles (9.7 km) from this point north. Once State Route 73 enters Scioto County, it is designated as the Scenic Scioto Heritage Trail by the Ohio Department of Transportation.

In combination with State Route 32, Route 73's easternmost 31 miles are part of the quickest route between Cincinnati and Portsmouth. Also Ohio state route 73 has turned into a bypass for Wilmington.