Pope Alexander IV was Pope from 12 December 1254 to his death in 1261.
Born as Rinaldo di Jenne, he was, on his mother's side, a member of the family de' Conti di Segni, the counts of Segni, like Pope Innocent III and Pope Gregory IX. His uncle Gregory IX made him cardinal deacon and Protector of the Order of Franciscans in 1227, Camerlengo of the Holy Roman Church from 1227 until 1231 and Bishop of Ostia in 1231 (or 1232). He became Dean of the Sacred College of Cardinals in 1244 (or 1240). On the death of Pope Innocent IV in 1254 he was elected pope at Naples on 12 December 1254.
Alexander IV succeeded Innocent IV as guardian of Conradin, the last of the Hohenstaufens, promising him protection; but in less than three weeks he conspired against him and bitterly opposed Conradin's uncle Manfred. Alexander IV threatened excommunication and interdict against the party of Manfred without effect. Nor could he enlist the kings of England and Norway in a crusade against the Hohenstaufens. Rome itself became too Ghibelline for the Pope, who withdrew to Viterbo, where he died in 1261. He was buried in Viterbo Cathedral, but his tomb was destroyed during sixteenth-century renovations.
Alexander's pontificate was signaled by efforts to reunite the Eastern Orthodox churches with the Catholic Church, by the establishment of the Inquisition in France, by favours shown to the mendicant orders, and by an attempt to organize a crusade against the Tatars after the second raid against Poland in 1259.