State Route 561 (SR 561) is a north–south state highway in the southwestern portion of the U.S. state of Ohio. Its southern terminus is at U.S. Route 50 approximately 9 miles (14 km) east of Downtown Cincinnati – this point also serves as the western termini for both State Route 32 and State Route 125; the route’s northern terminus is at its intersection with State Route 4. The route takes many different names along its length, being first known as Linwood Avenue, Observatory Avenue, and Edwards Road in Cincinnati; then it is named Smith Road and Carthage Avenue as it passes through Norwood; its final stretch in Cincinnati once again is as Seymour Avenue.

No part of SR 561 in Ohio is included as a part of the National Highway System (NHS). The NHS is a network of highways that are identified as being most important for the economy, mobility and defense of the nation.

SR 561 heads north from the southern terminus at an interchange with US 50. The route heads northwest turning north towards Interstate 71. After I–71, the road has an short concurrency with US 22/SR 3 in Norwood. The road heads towards the northern terminus at Vine Street, passing through a traffic light at SR 4 (Paddock Road) just south of exit 9 of I–75.

The entire route is in Hamilton County.