State Route 109 (abbreviated SR 109) is a 26.24-mile (42.23 km) long state highway located in York County, Maine. Its southern terminus is at U.S. Route 1 and State Route 9 in Wells. Its northern terminus is at the New Hampshire border in Acton, where it connects to New Hampshire Route 109. It is a multi-state route with NH 109. NH 109 is signed as a north–south highway, but occupies a southeast-to-northwest alignment. Major towns and cities along the length of SR 109 include Wells and Sanford.