Route 12 is a state highway located in Hunterdon County, New Jersey, United States. It runs from the Uhlerstown-Frenchtown Bridge at the Delaware River border with Pennsylvania in Frenchtown east to an intersection with U.S. Route 202 (US 202) and Route 31 at the Flemington Circle in Flemington. The route is mostly a two-lane undivided road that passes through rural areas of woodland and farmland. It intersects Route 29 and County Route 513 (CR 513) in Frenchtown, CR 519 in Kingwood Township, CR 579 on the border of Delaware Township and Raritan Township, and CR 523 in Raritan Township.