Pennsylvania Route 405 (PA 405) is a 35.124-mile-long (56.527 km) state highway that runs in the north-central part of the U.S. state of Pennsylvania. The southern terminus of PA 61 in Sunbury. The route heads across the Susquehanna River to Northumberland and northward along the West Branch Susquehanna River through Milton, Watsontown and Muncy until entering Hughesville, where it terminates at an intersection with U.S. Route 220 (US 220).