Who invented the catapult?

The catapult was invented by engineers working under Dionysios of Syracuse in approximately 399 B.C. The first catapult design was small and closely resembled an early Medieval crossbow that used a released trigger to launch missiles.

During the last quarter of the third century B.C., Archimedes of Syracuse made improvements in catapult design, enabling catapults to launch stones that weighed up to 1800 pounds. This weapon was used during a siege of the city, causing damage to the invading fleet. A report of the event found in Polybius Book VIII indicates that the Archimedes catapult came in several sizes, allowing it to strike at an enemy over different distances.