Mark IX or Mark 9 often refers to the ninth version of a product, frequently military hardware. "Mark", meaning "model" or "variant", can be abbreviated "Mk."
Mark IX or Mark 9 may refer to:
Technology Military and weaponry BL 9.2 inch gun Mk IX–X (1899), a British 9.2 inch coastal defence cannon Armstrong Whitworth 12-inch 40-calibre naval gun Mark IX (1901), a British naval gun that was later used on land in the BL 12 inch Railway Gun 21in Mk IX torpedo, a British 21-inch torpedo Bliss-Leavitt Mark 9 torpedo (1915), an American 21-inch torpedo Mark IX tank, a World War I troop-carrying tank—the first armoured personnel carrier Ordnance QF 2 pounder (1936–1945), British mounted gun used in World War II Supermarine Spitfire Mk IX, the second most numerous Spitfire variant Floro MK-9 (2001), a submachine gun designed and built in the Philippines W9 (nuclear warhead), nuclear artillery shell
Vehicles Jaguar Mark IX (1959–1961), a British luxury car Lincoln MK9 (2001), an American concept car Cooper Mark IX, a Formula Three racing car
Other uses Mark 9 or Mark IX, the ninth chapter of the Gospel of Mark in the New Testament of the Christian Bible Mark IX Hawk, a fictional spacecraft in the Space 1999 TV series