State Route 5 is part of Maine's system of numbered state highways, running from an intersection with Route 9 in Old Orchard Beach, to an intersection with Route 120 in Andover. Route 5 is 118.1 miles (190.1 km) long.

From its southern terminus near the Pier in Old Orchard Beach, Route 5 leaves the town to the west, going towards the neighboring city of Saco. The route runs northwest from Saco, passes very briefly through a Northwest corner of Biddeford, and intersects U.S. Route 202 near the Lyman-Waterboro line. Route 5 runs concurrently with U.S. 202 for a short distance to East Waterboro.

Between Waterboro and Cornish, Route 5 is known as the Sokokis Trail. North of Cornish, the highway follows the Saco River, crossing it at Hiram, to the town of Fryeburg. Route 5 continues north through Lovell to Bethel, where it intersects U.S. Route 2. The two routes run together along the Androscoggin River to Rumford Point in the town of Rumford, where Route 5 leaves to the north. It follows parallel to the west bank of the Ellis River to the route's end in Andover.

Route 5A is a short 3-mile (4.8 km) loop off Route 5 in Lovell.