State Route 590 (SR 590, OH 590) is a north–south state highway in the northwestern portion of the U.S. state of Ohio. The southern terminus of State Route 590 is at a signalized intersection with State Route 12 in the village of Bettsville. Its northern terminus is at a T-intersection with State Route 2 just south of Ottawa National Wildlife Refuge, and approximately 5 miles (8.0 km) north of Rocky Ridge.

Along its path, State Route 590 travels through portions of Seneca, Sandusky and Ottawa Counties. No portion of the highway is included as a part of the National Highway System.

State Route 590 was created in 1937. Its original routing consisted of the following: the current State Route 53 from its intersection with Seneca County Road 51 southwest of the unincorporated community of Old Fort to its intersection with Seneca County Road 61; County Road 61 from State Route 53 to the current southern terminus of State Route 590 at State Route 12 in Bettsville; and the entirety of the current routing of State Route 590. The portions of current State Route 53 and County Road 61 noted would only be designated as State Route 590 for one year. In 1938, State Route 590 was truncated to its current southern terminus at State Route 12, and the portion east of Bettsville would become part of re-routing of State Route 113.