S43

S43 may refer to:

Submarines

 * HMS Unicorn (S43), of the Royal Navy
 * INS Vagsheer (S43), of the Indian Navy
 * USS S-43 (SS-154), of the United States Navy

Other uses

 * County Route 563 (New Jersey), designated New Jersey Route S43 until 1953
 * County Route S43 (Bergen County, New Jersey)
 * Harvey Airfield, in Snohomish, Washington, United States
 * Sikorsky S-43, an American flying boat
 * Sulfur-43, an isotope of sulfur
 * S43, a postcode district in Chesterfield, England