Leonardo da Vinci designed a catapult that used a spring-powered arm to throw stones.
Leonardo's notebooks contain studies of siege engines, including a catapult with a large flexible spring mechanism. Twisting or loading the spring stored energy, which could then be released to drive the throwing arm forward. The design reflects his interest in increasing the power and reliability of military machinery.
A catapult is a broad class of siege engine that launches a projectile. A trebuchet instead uses a counterweight or traction system, while a ballista resembles a very large mechanical bow. These devices are related but are not interchangeable names for Leonardo's spring design.
Leonardo worked on such military concepts while seeking employment as an engineer and designer. His drawings often emphasize mechanisms and proportions, but surviving evidence does not show that every sketched machine was constructed or tested.