State Route 303 is an east–west state highway in northern portion of the U.S. state of Ohio. Its western terminus is at U.S. Route 20 in Wakeman, and its eastern terminus is 1.28 miles (2.06 km) east of Windham. Signage photos from 2003 showed that the route apparently ended at State Route 534 and was co-signed with State Route 82 (this concurrency would be less than ½ mile). In fact, before the construction of the Ohio Turnpike, State Route 303 did intersect with State Route 534, as seen in highway maps from 1940. However the Technical Straight Line Diagram for State Route 303 in Trumbull County shows that SR 303 now ends at State Route 82, and signs now reflect that fact.

State Route 303 passes through Cuyahoga Valley National Park. East of Richfield, a widened section of road with left turn lanes that apparently go nowhere reveals the former site of the Richfield Coliseum.