Leonardo da Vinci designed an early ball bearing using rows of metal balls between rings.
Around 1498, Leonardo studied a bearing in which balls could roll between a rotating inner ring and a stationary outer ring. The rolling elements reduced sliding friction and helped prevent the balls from crowding together. His drawing is one of the earliest known designs for a modern-style ball bearing.
Leonardo’s bearing was part of his broader mechanical studies, which examined gears, axles, friction, and motion. The principle is straightforward: rolling contact generally creates less resistance than sliding contact. That makes it easier for a shaft or wheel to rotate.
Leonardo did not create the mass-produced bearings used in modern machines. Industrial ball bearings became practical much later, after improvements in precision manufacturing and steel production. His design is therefore best understood as an important early concept, not as the direct origin of every later bearing.