S56 may refer to:
Aircraft Blériot-SPAD S.56, a family of prototype French airliners Savoia-Marchetti S.56, an Italian flying boat Sikorsky S-56, an American helicopter Sukhoi S-56, a proposed Russian carrier fighter
Other uses S56 (Long Island bus) S56 (New York City bus) serving Staten Island County Route S56 (Bergen County, New Jersey) Explorer S-56 (satellite), a failed American spacecraft GER Class S56, a British steam locomotive , a submarine of the Indian Navy Prince Skyline (S56), a Japanese automobile S56: Dispose of this material and its container at hazardous or special waste collection point, a safety phrase
Siemens S56, a Siemens mobile phone