Pope Nicholas III (Latin: Nicolaus III; c. 1225 – 22 August 1280), born Giovanni Gaetano Orsini, was head of the Catholic Church and ruler of the Papal States from 25 November 1277 to his death on 22 August 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 (1243–1254), protector of the Franciscans by Pope Alexander IV (1254–1261), inquisitor-general by Pope Urban IV (1261–64), and succeeded Pope John XXI (1276–1277) after a six-month vacancy in the Holy See resolved in the papal election of 1277, largely through family influence.