State Route 423 (SR 423) is a 17.07-mile (27.47 km) long north–south state highway in the central portion of the U.S. state of Ohio. The southern terminus of SR 423 is in Waldo at a T-intersection that also serves as the eastern terminus of SR 47, as well as the southern terminus of SR 98. The signed northern terminusof SR 423 is at its junction with SR 231 nearly 3 miles (4.8 km) east of Morral.