New Hampshire Route 171 (abbreviated NH 171) is a 15.194-mile-long (24.452 km) east–west highway in southern Carroll County in the Lakes Region of New Hampshire.

The two-lane highway heads east as Mountain Road, which passes along the southern flank of the Ossipee Mountains, including Mount Roberts, Turtleback Mountain, and Mount Shaw, and by the Castle in the Clouds.

NH 171 continues through the town of Tuftonboro, where the route crosses the Melvin River and passes to the south of Dan Hole Pond.

NH 171 crosses the Beech River in Water Village, then climbs over high ground south of Thompson Hill and intersects NH 28 west of Ossipee Corner, the town center of Ossipee.

The highway parallels Poland Brook east of Ossipee Corner and reaches its eastern terminus at NH 16 (White Mountain Highway) just north of that highway's crossing of Poland Brook.