S56

S56 may refer to:

• S56: Dispose of this material and its container at hazardous or special waste collection point, a safety phrase in chemistry
• S56 (New York City bus) serving Staten Island
• S-56 submarine, a Soviet S class submarine
• Blériot-SPAD S.56, a family of prototype French airliners
• County Route S56, a county route in Bergen County, New Jersey
• The Great Eastern Railway S56, later reclassified as the LNER J69
• INS Sindhudhvaj (S56), a 1987 Sindhughosh class submarines of the Indian Navy
• Savoia-Marchetti S.56, a 1924 Italian single-engine biplane flying boat trainer and tourer
• Siemens S56, a Siemens mobile phone
• Sikorsky S-56, a 1953 cargo helicopter
• Sukhoi S-56, a shipborne light fighter aircraft part of a series of designs by Sukhoi