Mark XIII or Mark 13 often refers to the 13th version of a product, frequently military hardware. "Mark", meaning "model" or "variant", can be abbreviated "Mk."
Mark XIII or Mark 13 may refer to:
Science Kallikrein 13 or mK13, a protein
Military and weaponry Mark 13 torpedo, US Navy's most common air-dropped torpedo in World War II Mk XIII railway gun, a variant of the British BL 9.2-inch railway gun Supermarine Spitfire PR Mk XIII, lightly armed low-altitude Rolls-Royce Merlin-powered reconnaissance aircraft, first tested March 1943 Vickers Wellington GR Mk XIII, 1944 Coastal Command medium bomber with ordinary nose turret, mast radar and no waist guns De Havilland Mosquito NF Mk XIII, a night fighter variant of the De Havilland Mosquito that replaced nose guns with radar Mark 13 nuclear bomb (1951–1954), an American experimental weapon that never entered service Centurion Mk 13 (1959–1962), a British main battle tank fitted with infrared equipment and a ranging gun Mk 13 missile launcher, a single-arm guided missile launching system Mk 13 Mod 0 or EGLM (2004), a 40 mm grenade launcher MK 13 rifle, a US Military sniper rifle MK13-class missile boat, a vessel of the Iranian Islamic Revolutionary Guard Corps Navy
Technology Cooper Mk XIII (1959), a Cooper 500 cc rear-engined racing car
Other uses Mark 13 and Mark XIII, the thirteenth chapter of the Gospel of Mark in the New Testament of the Christian Bible M.A.R.K. 13, the fictional killer robot in the 1990 film Hardware