Rainalducci was born at Corvaro, an ancient stronghold near Rieti in Lazio. He joined the Franciscan order after separating from his wife in 1310, and became famous as a preacher. He was elected through the influence of the excommunicatedEmperor, Louis IV the Bavarian, by an assembly of priests and laymen, and consecrated at St. Peter's Basilica in Rome on May 12, 1328 by the bishop of Venice. After spending four months in Rome, he withdrew with Louis IV to Viterbo and then to Pisa, where he was guarded by the imperial vicar. On February 191329 Nicholas V presided at a bizarre ceremony in the Duomo of Pisa, at which a straw puppet representing Pope John XXII and dressed in pontifical robes was formally condemned, degraded, and handed over to the secular arm. Nicholas V was excommunicated by John XXII in April 1329, and sought refuge with Count Boniface of Donoratico near Piombino. Having obtained assurance of pardon, he presented a confession of his sins first to the archbishop of Pisa, and then at Avignon on August 25, 1330 to John XXII, who absolved him.
He remained in honourable imprisonment in the papal palace, Avignon until his death in October 1333.