State Route 664 (SR 664) is a north–south state highway in the southern portion of the U.S. state of Ohio. The highway has its southern terminus at a T-intersection with SR 56 in the unincorporated community of South Bloomingville. The northern terminus of SR 664 is also at a T-intersection, this time with SR 256 on the Fairfield–Perry county line approximately 4.75 miles (7.64 km) north of the village of Rushville.