State Route 129 (SR 129) is part of Maine's system of numbered state highways, located in southern Lincoln. It is one of several routes which "dead-end" on the Atlantic coast at their southern ends. The southern terminus of SR 129 is at Middle Road in South Bristol, a few miles north of at the tip of South Bristol. The northern terminus is located at U.S. Route 1 Business (US 1 Bus.) in Damariscotta, an end it shares with SR 130. It runs for 13.36 miles (21.50 km).