Route 173 is a state highway in New Jersey, United States that is a designation for an old section of U.S. Route 22. The route runs 14.62 mi (23.53 km) from Interstate 78 and U.S. Route 22 in Greenwich Township, Warren County to County Route 626 (Beaver Avenue) in Clinton Township, Hunterdon County, just east of an interchange with Route 31. Route 173 parallels Interstate 78 and U.S. Route 22 for its entire length through rural areas of Warren and Hunterdon Counties, passing through the towns of Bloomsbury and Clinton along the way. At one point just to the west of Clinton, Route 173 runs concurrent with Interstate 78 and U.S. Route 22.