State Route 172 or SR-172 is a 24.420-mile (39.300 km) state highway that serves as an east-west connection between Vina and Bear Creek through Franklin and Marion Counties. SR-172 intersects SR-19 at its western terminus and SR-13 at its eastern terminus.

State Route 172 begins at its intersection with AL-19 in Vina. From this point, SR-172 travels in a southeasterly direction where it meets SR-187 in Hodges. From Hodges, the route continues generally in its eastern direction and intersects US-43 in Hackleburg. From this point, SR-172 again continues generally in an easterly direction and intersects SR-237, in addition to sharing a .435-mile (0.700 km) concurrency with SR-241, prior to reaching its eastern terminus at SR-13 in Bear Creek.