Cardinal Stefaneschi was a Roman aristocrat and a graduate of Paris University. He composed poems on the election, abdication and canonization of Celestine V and the coronation of Boniface VIII. He later moved to Avignon, where he lived uneventfully until his death in 1341. Early recognizing the brilliant young Giotto, he commissioned two prestigious works for Saint Peter’s. Little survives of the monumental Navicella mosaic, one of the most revolutionary works of European art. Giotto’s second commission, the double-sided high altarpiece still survives. It set new standards for patron’s portraits and historical representations of martyrdom, and was also a manifesto of Giotto’s colour. The early dating proposed here is buttressed by new evidence. In Avignon Stefaneschi turned to poetry, liturgy and music. He commissioned the Master of the Codex of Saint George. More significant still was his championing of Simone Martini, who frescoed the Madonna of Humility in Avignon cathedral. Stefaneschi’s patronage impacted on Robert of Anjou and cardinals Napoleone Orsini and Guillaume Godin. The octogenarian cardinal re-emerged as creative patron of the greatest painters of the age.