State Route 703 (SR 703) is a state highway in western Ohio. Its western terminus is in Montezuma at SR 219, and its eastern terminus is in St. Marys at an intersection with SR 29, SR 66, and the southern terminus of SR 116 in St. Marys. The route is mainly an east–west highway along the shores of Grand Lake St. Marys, although the section between Celina and Montezuma travels in a more north-south fashion.