Type 91 may refer to:
Japanese war equipment Hiro Navy Type 91 flying boat, or Hiro H4H, a 1930s Japanese bomber or reconnaissance monoplane flying boat Nakajima Army Type 91 fighter, a Japanese fighter of the 1930s Type 91 air-to-ship missile, a Japanese air-to-ship missile Hiro Type 91 (engine), a 12-cylinder aircraft engine used by the Imperial Japanese Navy in the mid-1930s Type 91 grenade, an improved version of the Type 10 hand grenade of the Imperial Japanese Army Type 91 10 cm howitzer, used by the Imperial Japanese Army during the Second Sino-Japanese War and World War II Type 91 surface-to-air missile, a Japanese man-portable surface-to-air missile system Type 91 torpedo, an aerial torpedo of the Imperial Japanese Navy
Other T91 assault rifle, a Taiwanese assault rifle Type 91 grenade launcher, a Chinese grenade launcher used to launch 35mm non-lethal grenades Bristol Type 91 Brownie, a British light sports aircraft