jats:p This article provides the first comprehensive study of the material relating to sliding bearings, lubrication and wear within the writings of Leonardo da Vinci (1452–1519). While in many instances he was evidently describing contemporary practice, in other cases he demonstrated great innovation and insight. His descriptions of plain journal and pivot bearings and their materials are far richer than those of any other Renaissance engineer. His ability to classify and analyse his observations led him to highly perceptive conclusions about the effect of loading direction on wear rate and the mechanisms of wear in sliding contacts. In deducing the dependence of wear on load and sliding duration, Leonardo's thinking anticipated that of Reye, Preston and Archard by more than 350 years. </jats:p>