State Route 73 (SR 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 at the intersection of SR 732. SR 73’s eastern terminus is in Portsmouth at US 23; this is also the southern terminus of SR 104, and the two state routes run concurrent for over 6 miles (9.7 km) from this point north.