Nicholas III. (Giovanni Gaetano Orsini), pope from November 25, 1277 to August 22, 1280, was a Roman nobleman who had served under eight popes, been made cardinal-deacon of St Nicola in carcere Tulliano by Pope Innocent IV., protector of the Franciscans by Pope Alexander IV., inquisitor-general by Pope Urban IV., and succeeded Pope John XXI., largely through family influence, after a six-months' vacancy in the Holy See. His brief pontificate was marked by several important events. A born politician, he greatly strengthened the papal position in Italy. He concluded a concordat with Rudolph I of Habsburg in May 1278, by which the Romagna and the exarchate of Ravenna were guaranteed to the pope; and in July he issued an epoch-making constitution for the government of Rome, which forbade foreigners taking civil office. Nicholas issued the bull Exiit on the 14th of August 1279 to settle the strife within the Franciscan order between the parties of strict and loose observance. He repaired the Lateran palace and the Vatican at enormous cost, and erected a beautiful country house at Soriano near Viterbo. Nicholas, though a man of learning and strength of character, brought just reproach on himself for his efforts to found principalities for his nephews and other relations. He died from a stroke of apoplexy.

from a 1911 encyclopedia

On a side note, Dante in 'The Inferno' from 'The Divine Comedy' talked briefly to Pope Nicholas III, who was condemned to spend eternity in the Eight Circle, Third Bolgia of Hell, reserved for Simoniacs.

Preceded by:
Pope John XXI
List of popes Succeeded by:
Pope Martin IV