Leonardo da Vinci sketched a ball bearing in 1498 as a friction-reducing mechanical component.
His drawing showed balls arranged inside a cage, allowing moving surfaces to roll rather than slide against one another. This arrangement is recognizably similar to the principle used in modern rolling-element bearings.
Leonardo was not documenting a mass-produced industrial bearing. His notebooks explored ways to reduce friction in machines, including rotating shafts and other mechanisms. The design is therefore best understood as an early recorded bearing concept, not the invention of the complete modern bearing industry.
A common mix-up is calling the sketch a modern ball-bearing assembly. Later engineers developed standardized races, cages, materials, lubrication, and manufacturing methods. Leonardo’s importance lies in recording the rolling-ball principle centuries before precision bearings became common in machinery.