Leonardo da Vinci is often credited with sketching an early form of the ball bearing.
Around 1498, Leonardo studied ways to reduce friction between moving surfaces. One drawing shows balls arranged so that they would roll rather than slide, allowing an upper component to move more freely around a lower one. This arrangement is recognizable as an early ball-bearing concept.
The historical claim needs careful wording. Leonardo did not invent every rolling-element bearing, and ancient and medieval technologies had already used rollers and related methods. His importance is that he clearly documented a compact arrangement of balls intended to prevent them from rubbing together and locking.
Modern ball bearings use precisely shaped races, cages, lubrication, and tightly controlled materials. Leonardo’s sketch lacked those industrial refinements, but it anticipated the key principle used in machinery, vehicles, electric motors, and countless other devices.