Leonardo da Vinci sketched an early ball bearing to reduce friction between moving surfaces.
Around 1498, Leonardo drew a bearing design in which balls moved between two rings. The balls were intended to keep the rings apart while allowing one ring to rotate smoothly against the other. This arrangement is recognizably related to the modern ball bearing.
Leonardo did not invent every later feature of industrial bearings, and his sketch was not a mass-produced machine. Modern ball bearings use carefully manufactured races, balls, cages, seals, and lubricants. The cage is especially important because it keeps the balls separated rather than letting them rub together.
A common mix-up is calling Leonardo’s drawing the first complete modern bearing. It is more accurate to describe it as an early recorded ball-bearing concept. His design belongs to a wider collection of Renaissance engineering studies that explored ways to reduce friction in machines.