State Route 412 (SR 412) is an east–west state highway in northern Ohio. The western terminus of State Route 412 is just northeast of Fremont at a diamond interchange with the U.S. Route 20/State Route 19 duplex, which follows the Fremont Bypass at that point. The eastern terminus of the state highway is at a T-intersection with State Route 101 approximately 3 miles (4.8 km) southwest of Castalia.