State Route 127 or SR-127 is a 13.510-mile (21.742 km) state highway that serves the north, central areas of Limestone County. SR-127 intersects SR-99 at its southern terminus in Athens and continues as Tennessee State Route 166 upon entering Tennessee at its northern terminus.

State Route 127 begins at its intersection with SR-99 in northern Athens. From this point, the route travels in a northerly direction before turning in a northwesterly direction north of Elkmont. SR-127 continues in its northwesterly path in crossing the Elk River prior to reaching the state line and continues as TN-166.

The entire route is in Limestone County.