New York State Route 12D (NY 12D) is a north–south state highway located in the northern part of New York in the United States. The southern terminus of the route is in the Oneida County village of Boonville, where it intersects NY 12. The northern terminus is at a junction with NY 12 in the Lewis County village of Lyons Falls. NY 46 and NY 294 are also present in the immediate area of the route's southern terminus.

New York State Route 12 (NY 12) is a state highway extending for 222.27 miles (357.71 km) through central and northern New York in the United States. The southern terminus of the route is at U.S. Route 11 (US 11) in the town of Chenango in the Southern Tier. The northern terminus is at NY 37 near the village of Morristown in the North Country. In between, the route serves three cities of varying size: Norwich, Utica, and Watertown. NY 12 intersects several primary routes, including US 20 in Sangerfield, New York State Thruway via Interstate 790 (I-790) in Utica, overlaps NY 28 from Barneveld to the town of Remsen, NY 3 in Watertown, and I-81 in Pamelia and Orleans.