Leonardo da Vinci used the ball-bearing concept to reduce friction between moving surfaces.
In his mechanical studies, Leonardo explored balls placed between surfaces so that sliding friction could be replaced by rolling motion. One of his drawings from around 1498 shows a bearing arrangement in which balls are separated so they can move with less interference. The idea could support rotating shafts and other machinery.
Leonardo did not invent every form of bearing, and ancient engineers had used rollers and related devices earlier. His importance is that he analyzed and illustrated a compact rolling-bearing principle during the Renaissance. The drawing is often cited as an early step toward the modern ball bearing.
Modern ball bearings use carefully manufactured balls, races, cages, and lubricants. Leonardo’s proposal was far less refined, and materials and manufacturing precision limited what could be built in his time. Still, the central mechanical insight remains the same: rolling contact generally produces less resistance than sliding contact.