State Route 178 is a 1.956-mile (3.148 km) long route in Clarke County in the southwestern part of the state. The western terminus of the route is at its junction with US-43 north of Grove Hill. The route ends at the city center of Fulton.

State Route 178 is a 2-mile-long (3.2 km) spur of US-43. Traveling east from US-43, the route travels along a two-lane road, connecting the small town of Fulton to the U.S. highway.

The entire route is in Fulton, Clarke County.