Nicholas II, né Gerard of Burgundy (died either July 19 or July 27, 1061), pope from December 1058 to July 1061, was at the time of his election Bishop of Florence.

He was set up by Hildebrand, with the support of the empress-regent Agnes of Poitou and of the powerful Duke Godfrey of Lorraine , against Benedict X, the nominee of the Roman nobles, and was crowned at Rome, after the expulsion of Benedict, on January 24 1059; His pontificate was signalized by the continuance of the policy of ecclesiastical reform associated with the name of Hildebrand (afterwards Gregory VII).

To secure his position he at once entered into relation with the Normans, now firmly established in southern Italy, and later in the year the new alliance was cemented at Melfi , where Nicholas II, accompanied by Hildebrand, Cardinal Humbert and the abbot Desiderius of Monte Cassino, solemnly invested Robert Guiscard with the duchies of Apulia, Calabria and Sicily, and Richard of Aversa with the principality of Capua, in return for oaths of fealty and the promise of assistance in guarding the rights of the Church.

The first fruits of this arrangement, which was based on no firmer foundation than the forged "Donation of Constantine", but destined to give to the papacy a position of independence towards both the Eastern and Western Empires, was the reduction in the autumn, with Norman aid, of Galera , where the antipope had taken refuge, and the end of the subordination of the papacy to the Roman nobles.

Meanwhile, Peter Damian and Bishop Anselm of Lucca had been sent by Pope Nicholas to Milan to adjust the difference between the Patarenes and the archbishop and clergy. The result was a fresh triumph for the papacy, Archbishop Wido, in face of the ruinous conflict in the Church of Milan, being forced to submit to the terms proposed by the legates, which involved the principle of the subordination of Milan to Rome; the new relation was advertised by the unwilling attendance of Wido and the other Milanese bishops at the council summoned to the Lateran palace in April 1059. This council not only continued the Hildebrandine reforms by sharpening the discipline of the clergy, but marks an epoch in the history of the papacy by its famous regulation of future elections to the Holy See.