Leonardo da Vinci designed an early ball bearing that used rolling balls to reduce friction between moving surfaces.
Around 1498, Leonardo studied bearings and drew a device in which balls moved within a ring. A separator kept the balls apart, allowing them to roll instead of slide against one another. This arrangement addressed a practical problem in machines: direct contact between surfaces creates friction, heat, and wear.
The sketch is frequently described as an early ball-bearing design, although it was not a modern standardized bearing and there is no evidence that Leonardo manufactured it at scale. His mechanism also included a screw-like arrangement intended to help the balls circulate.
Ball bearings later became essential in clocks, bicycles, electric motors, turbines, and many other machines. A common mix-up is to credit Leonardo with inventing the modern industrial ball bearing itself. More precisely, he documented an important early concept centuries before mass-produced bearings became practical.