Leonardo da Vinci designed a giant crossbow intended to launch exceptionally large projectiles.
The weapon appears in Leonardo’s studies of military engineering. Its bow was drawn on a very large scale, and the design included a broad supporting frame and mechanisms intended to help draw and release the string. Leonardo emphasized both the impressive size of the weapon and the engineering needed to make it operate.
The giant crossbow was a proposal, not a weapon known to have been built and used in battle. Its purpose was probably psychological as well as destructive: a spectacular machine could frighten an enemy even if its practical performance was limited.
It should not be confused with Leonardo’s smaller crossbow studies or with ancient ballistae. A ballista is a separate torsion-powered weapon, while Leonardo’s design is conventionally identified as a giant crossbow because it uses a large bow and string.