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.