1225 – 22 August 1280), born Giovanni Gaetano Orsini, was Pope from 25 November 1277 to his death in 1280.
He was a Roman nobleman who had served under eight popes, been made Cardinal-Deacon of St.
Nicola in Carcere Tulliano by Pope Innocent IV (1243–54), protector of the Franciscans by Pope Alexander IV (1254–61), inquisitor-general by Pope Urban IV (1261–64), and succeeded Pope John XXI (1276–77) after a six-month vacancy in the Holy See resolved in the papal election of 1277, largely through family influence.