Leonardo da Vinci is often credited with sketching an early ball-bearing design using nested rings and rolling balls.
His notebooks contain a mechanism in which balls move between rings, reducing direct sliding contact. The principle is to replace sliding friction with rolling friction, making rotation easier and reducing wear. Leonardo’s design is usually dated to the late fifteenth century.
The historical claim should be stated carefully. Leonardo did not invent every form of bearing, and ancient and medieval engineers used rollers, pivots, and other low-friction arrangements. His importance is that he clearly documented a recognizable ball-bearing concept.
Modern ball bearings add carefully manufactured races, cages, seals, and hardened steel or ceramic balls. Leonardo’s sketch lacked the precision manufacturing needed for dependable modern applications. The design nevertheless anticipated a central principle used in machinery, vehicles, turbines, and many other devices.