Leonardo di Piero Dati (1360 – 16 March 1425) was an Italian friar and humanist. He was Master General of the Dominican Order from 1414 to his death. He was a Prior of Santa Maria Novella from 1401, and took part in the Council of Pisa of 1409. Dati was the head of the Dominicans belonging to the Roman obedience during the Great Schism. At the time of the Council of Constance, Dati became Master General of a reunited Dominican Order. Dati then focused on the internal reform of the order, authoring the tract Lamentationes de regularibus observantiis lapsis, in which he expressed strong dissatisfaction with the laxity and confusion of the order. His sermons at Pisa and Constance include references to literary texts, and he was well known as an author of commentaries on Aristotle. Leonardo al