New Hampshire Route 120 is a 26.928-mile-long (43.336 km) secondary north–south state highway in Sullivan and Grafton counties in the upper Connecticut River Valley region of New Hampshire.

Its northern terminus is at New Hampshire Route 10 in Hanover.

The initial stretch of the highway is on North Street but then it turns onto Hanover Street and heads north, passing through the towns of Cornish and Plainfield with no major junctions.

NH 120 enters Lebanon and proceeds directly into the heart of the city, where it meets (and briefly overlaps) U.S. Route 4 at a large roundabout.

NH 120 is cosigned with NH 10 on North Park Street in Hanover to terminate at Lyme Road/College Street, but this does not appear to be part of the official routing.