Leonardo da Vinci sketched an early ball bearing using rolling balls between moving surfaces.
The purpose of a ball bearing is to reduce friction by replacing sliding contact with rolling contact. Leonardo's drawing, associated with his studies of friction around 1498, shows balls arranged in a way that helps prevent them from rubbing directly against one another while supporting movement.
The sketch is an important early bearing concept, but it was not a modern mass-produced bearing. Precision manufacturing, suitable materials, and reliable lubrication were needed before ball bearings became practical in machines and vehicles.
Leonardo was not the first person to use the general idea of rolling elements, and he did not create the modern industrial bearing standard. The historical claim is more specific: his notebooks contain an early recognizable design for a ball bearing.