State Route 566 (SR 566, OH 566) is a north–south state highway in eastern Ohio, a U.S. state. Located exclusively in northern Noble County, State Route 566 has its southern terminus at State Route 147, at a T-intersection 1.25 miles (2.01 km) north of the unincorporated community of Mount Ephraim. Its northern terminus is at another T-intersection, this time with State Route 285 approximately 1.25 miles (2.01 km) south of the village of Senecaville.