Leonardo da Vinci sketched a ball bearing using small rolling spheres to reduce friction between moving parts.
The concept appears in his engineering notebooks, where he explored ways to keep rotating components from rubbing directly against one another. Rolling elements can reduce sliding friction and help a shaft or mechanism move more freely.
Leonardo’s sketch is an early recorded design for a ball-bearing arrangement, but it was not the same as a modern standardized bearing manufactured with precisely finished races and hardened steel balls. His version also shows an understanding of a practical problem: the balls must be spaced so they do not bunch together.
Ball bearings later became important in clocks, machinery, bicycles, motors, and other rotating systems. Leonardo’s drawing is therefore best understood as an early engineering concept rather than the invention of the complete modern bearing industry.