S23

S23 may refer to:

Aircraft

 * Short S.23, a British flying boat
 * Sikorsky S-23, a Russian bomber

Land transport

 * S23 (Long Island bus), New York, U.S.
 * S23 (Rhine-Ruhr S-Bahn), Germany
 * Kita-Tatsumi Station, Osaka, Japan
 * Kutchan Station, Hokkaido, Japan

Law

 * Patent Reform Act of 2011, a failed bill of the U.S. Congress
 * S23: Do not breathe gas/fumes/vapour/spray (appropriate wording to be specified by the manufacturer), in the E.U. Dangerous Substances Directive

Medicine

 * S-23 (drug), a selective androgen receptor modulator
 * 40S ribosomal protein S23

Submarines

 * CHILEAN SUBMARINE Hyatt
 * HMS Repulse (S23), of the U.K.'s Royal Navy
 * INS Kalvari (S23), of the Indian Navy
 * INS Karanj (S23), of the Indian Navy
 * USS S-23 (SS-128), of the U. S. Navy

Other uses

 * 180 mm gun S-23, a Soviet heavy gun
 * British NVC community S23, a designation for swamp and fen habitats
 * Samsung Galaxy S23, a 2023 series of smartphones