The following highways are numbered 51:
Australia Kamilaroi Highway Plenty Road
Cambodia National Road 51 (Cambodia)
Canada Alberta Highway 51 (defunct) Saskatchewan Highway 51
Cuba
Caimito–Salado Road (2–51)
Finland Finnish national road 51
France A51 autoroute
Greece EO51 road
Hungary M51 expressway (Hungary)
India National Highway 51 (India)
Iran Zobahan Freeway Road 51
Italy Autostrada A51
Japan Japan National Route 51
South Korea
Lebanon 51M Coastal Highway
New Zealand New Zealand State Highway 51
Philippines N51 highway (Philippines)
South Africa
R51
Turkey , a motorway in Turkey running from Adana to Mersin.
United Kingdom British A51 (Kingsbury-Chester)
United States U.S. Route 51 Alabama State Route 51 Arizona State Route 51 Arkansas Highway 51 California State Route 51 (unsigned) Colorado State Highway 51 (1923-1968) (former) Florida State Road 51 County Road 51 (Hamilton County, Florida) Georgia State Route 51 Georgia State Route 51 (1920) (former) Hawaii Route 51 Idaho State Highway 51 Illinois Route 51 (former) Indiana State Road 51 Iowa Highway 51 K-51 (Kansas highway) Maryland Route 51 Maryland Route 51A Maryland Route 51B (former) Maryland Route 51C (former) Maryland Route 51D Maryland Route 51E Maryland Route 51F M-51 (Michigan highway) Minnesota State Highway 51 County Road 51 (Anoka County, Minnesota) County Road 51 (Ramsey County, Minnesota) Missouri Route 51 Nebraska Highway 51 Nebraska Link 51A Nebraska Link 51B Nebraska Link 51C Nebraska Recreation Road 51E Nebraska Recreation Road 51F Nebraska Recreation Road 51G Nebraska Recreation Road 51H Nevada State Route 51 New Hampshire Route 51 New Jersey Route 51 (former) County Route 51 (Bergen County, New Jersey) County Route S51 (Bergen County, New Jersey) County Route 51 (Monmouth County, New Jersey) New Mexico State Road 51 New York State Route 51 County Route 51 (Cayuga County, New York) County Route 51 (Dutchess County, New York) County Route 51 (Erie County, New York) County Route 51 (Essex County, New York) County Route 51 (Franklin County, New York) County Route 51 (Greene County, New York) County Route 51 (Herkimer County, New York) County Route 51 (Madison County, New York) County Route 51 (Oneida County, New York) County Route 51 (Orange County, New York) County Route 51 (Putnam County, New York) County Route 51 (Rensselaer County, New York) County Route 51 (Rockland County, New York) County Route 51 (Saratoga County, New York) County Route 51 (Schoharie County, New York) County Route 51 (Suffolk County, New York) County Route 51 (Sullivan County, New York) County Route 51 (Ulster County, New York) North Carolina Highway 51 Ohio State Route 51 Oklahoma State Highway 51 Oklahoma State Highway 51A Oklahoma State Highway 51B Oregon Route 51 Pennsylvania Route 51 Rhode Island Route 51 South Carolina Highway 51 Tennessee State Route 51 Texas State Highway 51 Texas State Highway Spur 51 Farm to Market Road 51 Texas Park Road 51 Utah State Route 51 Virginia State Route 51 Virginia State Route 51 (1928-1950) (former) West Virginia Route 51 West Virginia Route 51 (1920s) (former) West Virginia Route 51 (1930s) (former) Wisconsin Highway 51 (former) Wyoming Highway 51
Vietnam National Road 51 (Vietnam)
See also A51 (disambiguation)