Leonardo da Vinci designed an early ball-bearing concept to reduce friction between moving machine parts.
In Leonardo’s notebooks, a sketch shows balls arranged between two rings so that the rings can move with less sliding friction. The balls roll between the surfaces, replacing much of the rubbing motion with rolling motion. This is the basic principle of a ball bearing.
The drawing is often cited as an early bearing design, but Leonardo was not the first person ever to use rolling elements. Ancient and medieval engineers used rollers and other methods to move heavy objects. Leonardo’s importance lies in his clear study of a compact, reusable rolling-bearing arrangement.
Modern ball bearings require carefully manufactured rings, balls, cages, lubrication, and seals. Leonardo’s sketch lacked many of those later refinements. It therefore represents an early conceptual design, not a complete modern bearing assembly ready for industrial production.