S42

S42 may refer to :
* S42 (Berlin), a S-Bahn line
* , a safety phrase in chemistry
* S42 (Long Island bus)
* S42 (New York City bus), serving Staten Island
* S42 postcode for Chesterfield, North East Derbyshire
* Siemens S42, a 2000 variant of the tri-band mobile phone Siemens S40
* Sikorsky S-42, an 1930s American commercial flying boat
* USS S-42 (SS-153), a 1923 S-class submarine of the United States Navy