New York State Route 51 (NY 51) is a 55.02-mile-long (88.55 km) north–south state highway in the central part of the U.S. state of New York. The highway runs generally in a southwest to northeast direction from NY 8 in the hamlet of Mount Upton to north of the village of Ilion, where it ends at NY 5. NY 51 intersects several primary routes including, a short overlap with NY 23 in the village of Morris, a 2.8-mile (4.5 km) overlap with U.S. Route 20 (US 20) in Winfield, and NY 5S in Illion. NY 51 is a two-lane highway its entire length.