State Route 173 or SR-173 is a 14.462-mile (23.274 km) state highway that serves as a north-south connection between Headland and Abbeville in Henry County. SR-173 intersects US-431 at its southern terminus and SR-27 at its northern terminus.

State Route 173 begins at its intersection with US-431 in Headland. From this point, SR-173 travels briefly towards the southwest before turning to the north as it leaves the town. From Headland, SR-173 follows a northerly track through its northern terminus at SR-27.

The entire route is in Henry County.