Leonardo da Vinci is often credited with sketching an early ball-bearing design.
His mechanical studies included balls placed between moving surfaces so that friction could be reduced. The principle is simple: rolling contact generally creates less resistance than sliding contact. Leonardo used this idea in the broader development of machines, bearings, gears, and other mechanisms.
The sketches are associated with the Codex Madrid I and with Leonardo’s investigations into friction. They do not represent a complete modern bearing industry, which requires carefully manufactured races, standardized balls, lubrication, and precise tolerances.
Leonardo was not necessarily the first person to imagine rolling supports, and historical claims about invention can be too absolute. His importance is that he clearly studied and illustrated the principle in a sophisticated mechanical context. Modern ball bearings became practical much later as manufacturing technology improved.