New York State Route 345 (NY 345) is a state highway located entirely within St. Lawrence County in the North Country of New York in the United States. It is a north–south route connecting the towns of Waddington and Potsdam by way of the town of Madrid. The southern terminus of NY 345 is at an intersection with U.S. Route 11 (US 11) in the village of Potsdam. Its northern terminus is at a junction with NY 37 in the village of Waddington by the St. Lawrence River.