S40 may refer to:
Aircraft SABCA S.40, a Belgian trainer aircraft Sikorsky S-40, an American amphibious flying boat Spectrum S-40 Freedom, an American business jet
Automobiles Suzuki Boulevard S40, a Japanese motorcycle Toyota Crown (S40), a Japanese luxury car Volvo S40, a Swedish automobile
Electronics Canon PowerShot S40, a digital camera IBM NetVista S40, a personal computer Series 40, a software platform used in Nokia cell phones Siemens S40, a mobile phone
Rail and transit S40 (New York City bus), United States S40 (ZVV), a line of Zurich S-Bahn in the cantons of Schwyz and Zurich, Switzerland S40, a regional railway service of Treni Regionali Ticino Lombardia in Italy and Switzerland S40, a line of Vienna S-Bahn in Austria
Roads County Route S40 (Bergen County, New Jersey) New Jersey Route 72, designated Route S40 until 1953
Submarines
, a submarine of the Royal Navy , a submarine of the Indian Navy , a submarine of the United States Navy
Other uses S40 Racing, a 1997 freeware game S40: To clean the floor and all objects contaminated by this material use ... (to be specified by the manufacturer), a safety phrase Somua S40, a prototype French tank Sulfur-40, an isotope of sulfur S40, a postcode district in Chesterfield, England