State Route 109 is a 10-mile (16 km) long route in Houston County in the southeastern part of the state. The southern terminus of the route is at the Florida state line, where it serves as a continuation of Florida State Road 77. The northern terminus of the route is at its junction with U.S. Highway 231 north of Madrid.

State Route 109 is routed along a two-lane road for its existence. It serves as a connecting route between Dothan and Graceville, Florida, which is located approximately five miles south of the Alabama-Florida state line.

The entire route is in Houston County.