Leonardo da Vinci studied a ball bearing in a design using two concentric rings of balls.
The drawing is generally dated to the late fifteenth century and shows balls placed between two rings. The arrangement was intended to prevent the balls from touching one another while allowing relative movement between the rings. This reduces friction compared with sliding contact and represents the central principle of a rolling-element bearing.
Leonardo did not invent every later feature of the modern ball bearing, and his sketch was not a mass-produced industrial component. The design is significant because it demonstrates an early understanding of how rolling bodies can replace sliding surfaces. Standardized bearings became especially important much later, with advances in manufacturing, steelmaking, and machinery during the Industrial Revolution.