S42

S42 may refer to:

Aviation

 * Blériot-SPAD S.42, a French biplane trainer aircraft
 * Sikorsky S-42, an American flying boat
 * Springer Municipal Airport, in Colfax County, New Mexico, United States

Rail and transit

 * S42 (Berlin), a line of the Berlin S-Bah
 * S42 (Long Island bus)
 * S42 (New York City bus), serving Staten Island

Science

 * S-42 (geodetic datum), used in Eastern Europe
 * S42: During fumigation/spraying wear suitable respiratory equipment (appropriate wording to be specified by the manufacturer), a safety phrase
 * Sulfur-42, an isotope of sulfur

Submarines

 * ARA San Juan, of the Argentine Navy
 * HMS Ursula (S42), of the Royal Navy
 * INS Vagli (S42), of the Indian Navy
 * USS S-42 (SS-153), a submarine of the United States Navy

Other uses

 * IBM NetVista S42, a personal computer
 * Siemens S42, a mobile phone
 * Zulu language
 * S42, a postcode district in Chesterfield, England