State Route 355 (SR 355) was a short 1.37-mile-long (2.20 km) state highway in southwestern Ohio. The route served the former Fort St. Clair State Memorial (now Fort St. Clair Park) in Eaton, Preble County. The route began at SR 122 in western Eaton, traveled south along Camden Road for about 0.3 miles (0.48 km) before turning into the memorial, looping through the entire site, and ending at itself just south of the route's start at SR 122.