State Route 139 or SR-139 is a 19.856-mile (31.955 km) state highway that serves as a north-south connection between Maplesville and Montevallo. SR-139 intersects SR-22 at its southern terminus and SR-25 at its northern terminus.

State Route 139 begins at its intersection with SR-22 in Maplesville. From this point, SR-139 follows a northerly course through Bibb County in route to its northern terminus at SR-25 southwest of Montevallo in Shelby County.