State Route 243 (SR 243, OH 243) is an east–west state highway in the southern portion of the U.S. state of Ohio. The western terminus of State Route 243 is at a diamond interchange with the U.S. Route 52 expressway in Coal Grove. The eastern terminus of the state highway is at its signalized junction with State Route 7 approximately 1.25 miles (2.01 km) west of Proctorville near the northern banks of the Ohio River.

State Route 243 used to continue east from here, running concurrently with State Route 7 into Proctorville, then split briefly from State Route 7 as it passed through the community of Rome before ending at State Route 7 about 3 miles (4.8 km) east of Proctorville. State Route 243 was truncated to its present location following completion of the new State Route 775 by-pass of Proctorville, which State Route 7 was re-routed onto, leaving jurisdiction of the former routings of State Route 7 and State Route 243 through Proctorville and Rome to be turned over from the state to the local jurisdictions.

The entire route is in Lawrence County.