X9

X9 may refer to:
 * X9 (New York City bus)
 * X9, a Metrobus route
 * X-9 Shrike, a missile
 * ASC X9, the ANSI Accredited Standards Committee X9 (ASC X9)
 * Khors Aircompany, former IATA code
 * Former IATA code for WOW air
 * Secret Agent X-9, a comic strip (1934–1996) created by Dashiell Hammett
 * A binary star system located in 47 Tucanae.