New Hampshire Route 113B (NH 113B), despite its designation, is not a loop road of NH 113. The route, which never intersects nor comes close to NH 113, is a loop of Maine State Route 113, but lies almost entirely within New Hampshire, producing the very unusual situation of one state having a suffixed route off another state's highway.
Both ends of the highway are located in the town of Stow, Maine, while most of the route () runs in Chatham, New Hampshire.