New York State Route 12E (NY 12E) is a state highway located entirely within the northwestern part of Jefferson County in northern New York in the United States. The southern terminus is at NY 12F in the village of Brownville. Its northern terminus, both signed and official, is at NY 12 in the village of Clayton. While NY 12 follows a direct north–south routing between Watertown and Clayton, NY 12E diverges westward to follow the shoreline of Lake Ontario. The portion of NY 12E north of its junction with NY 180 is part of the Seaway Trail, a National Scenic Byway.