State Route 634 (SR 634) is a 17.95-mile-long (28.89 km) state highway in the northwestern portion of the U.S. state of Ohio. The highway runs from its southern terminus at its junction with SR 189 and SR 190 in Fort Jennings to its northern terminus at the intersection of SR 15 nearly 1.5 miles (2.4 km) north of Continental. SR 634 runs entirely within Putnam County and is entirely a two-lane highway.SR 634 was commissioned in the late 1930s, the northern terminus was in Defiance County.