Route 18 is a state highway in the central part of the US state of New Jersey. It begins at an intersection with Route 138 in Wall Township, Monmouth County, and ends at Interstate 287 (I-287) in Piscataway, Middlesex County. Route 18 is a major route through Central New Jersey that connects the Jersey Shore to the Raritan Valley region, connecting the seats of Monmouth County (Freehold) and Middlesex County (New Brunswick) respectively. The route runs through Ocean Township, Marlboro Township, East Brunswick, and is the main thoroughfare for Rutgers University. Much of the route is a freeway (including the entire portion in Monmouth County and much of the northern end through New Brunswick and Piscataway). The remainder of the route is an arterial road with traffic lights in the East Brunswick and Old Bridge Township areas, and a boulevard in the remainder of Piscataway. Route 18 was designated in 1939 as a proposed freeway from Old Bridge to Eatontown.
left|thumb|Route 18 northbound past the Route 79 interchange in Marlboro Township
A large interchange near the Naval Weapons Station Earle serves Industrial Way West, Wyckoff Road (CR 547), Route 36, Hope Road (CR 51), the Garden State Parkway, the Tinton Falls interchange (exit 105), and Wayside Road (CR 38). After passing over the Southern Secondary railroad line operated by the Delaware and Raritan River Railroad, the route continues northwestward into Colts Neck Township. The freeway continues to the northwest through wooded land for several miles, crossing over Normandy Road and to the south of the Pebble Creek Golf Club. Exits along this stretch include Route 34, Colts Neck Road (CR 537), Route 79, CR 520, and Tennent Road (CR 3), which connects to Freehold Borough and Marlboro Township.|group=lower-alpha|name="slds"