Route 138 is an arterial state highway located entirely in Monmouth County, New Jersey that extends for . The route's western terminus is at the eastern end of Interstate 195 at the interchange with Route 34 in Wall Township. Route 138's eastern terminus is at Route 35 in Wall Township. The highway is also meant to be an evacuation route in case of a disaster, where the eastbound lanes (as well as the eastbound lanes on Interstate 195) would be reversed all the way to the New Jersey Turnpike.