What weapon did Leonardo da Vinci design as a giant crossbow on a wheeled frame?

Leonardo da Vinci designed a giant crossbow as a large wheeled siege weapon.

The design appears in Leonardo’s codices and is much larger than an ordinary handheld crossbow. Its broad bow was mounted on a frame, while wheels and mechanical parts were intended to help move and operate the weapon. The design reflects Leonardo’s interest in combining engineering, military technology, and dramatic visual scale.

The crossbow is often described as a “giant crossbow” or “giant cross-bow.” It should not be confused with Leonardo’s other military studies, such as his armored vehicle, multi-barreled gun, or giant catapult. The surviving drawing is a design proposal rather than evidence that a working example was built.

Leonardo’s military inventions were generally conceived for powerful patrons, including rulers and city-states. Many remained on paper because their mechanisms were difficult to manufacture with Renaissance materials. The giant crossbow therefore matters chiefly as an example of Leonardo’s approach to mechanical design, not as a documented battlefield weapon.