Leonardo da Vinci's 33-barrel organ was a wheeled weapon with three rows of eleven barrels arranged to fire in sequence.
The design appears among Leonardo's military engineering studies. Its barrels were mounted on a broad frame, and the arrangement allowed one row to be aimed or fired while another could be prepared. The name “organ” refers to the visual resemblance between the parallel gun barrels and the pipes of a musical organ.
The weapon was intended to improve the rate of fire of small artillery in battle. A conventional cannon had to be loaded after every shot, while a multi-barrel system could produce a volley and then be repositioned or reloaded. It still would have been heavy, difficult to maneuver, and slow to reload compared with modern firearms.
Leonardo's drawing is a proposal, not evidence that he successfully manufactured the weapon. The design is also distinct from a modern machine gun: the barrels were fixed in groups, and the concept relied on sequential volleys rather than automatic loading and firing.