Nicholas V, Pietro Rainalducci († October 16 1333) was an antipope in Italy from May 12 1328 to July 25 1330 during the pontificate of Pope John XXII at Avignon.

Rainalducci was a native of Corvaro in the Abruzzi. 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 excommunicated emperor, 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 to Viterbo and then to Pisa, where he was guarded by the imperial vicar. On February 19 1329 Nicholas presided at a bizarre ceremony in the cathedral of Pisa, at which a straw puppet representing John XXII and dressed in pontifical robes was formally condemned, degraded, and handed over to the secular arm. Nicholas was excommunicated by Pope 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 (August 25, 1330) to the pope at Avignon. He remained in honourable imprisonment in the papal palace until his death in October 1333.