(2 Aug. 1057–29 Mar. 1058)
When the news of Victor II's unexpected death on 28 July 1057 reached Rome, the reform leaders there immediately consulted Frederick of Lorraine, abbot of Monte Cassino, about a successor. He proposed five names, including those of Hildebrand (later Gregory VII) and Humbert of Silva Candida (c.1000–61), but in the event was himself elected on 2 Aug. and consecrated next day; he took the name of Stephen I, whose feast fell on 2 Aug. No approach was made to the German imperial family, which had nominated the four previous popes, and this omission has been interpreted as an attempt to take advantage of the minority of Henry IV (1056–1106) and the weakness of Empress Agnes, the regent, to free the papacy from its control. A more likely explanation is that speedy action was deemed necessary to forestall any move by aristocratic Roman families to recover their influence in papal appointments; the fact that, if trouble arose, the pope chosen could rely on the support of his powerful brother Godfrey the Bearded, duke of Lorraine and count of Tuscany (c.1040–96), must have told in his favour. It is significant that a delegation led by Hildebrand reached the court at Pöhlde, in Saxony, in Dec., where it must have obtained retrospective approval of the choice that had been made.
Stephen's earlier career argued for a strong, progressive pontificate. Youngest son of Duke Gozelon I of Lorraine, educated at Liège, he had been a canon and then archdeacon there under bishops sympathetic to reform in the church. In 1049 he became dean of St Alban's, Namur. Leo IX, who probably met him at the reforming synod of Mainz in Oct. 1049, brought him to Rome as one of his close collaborators, making him chancellor on 9 Mar. and then librarian of the Roman church on 10 June 1051. He accompanied Leo on his campaign against the Normans, and was one of his legates to Constantinople in 1054. Although a leading member of the curia, he judged it prudent in 1055, in view of the forthcoming visit to Italy of Emperor Henry III (1039–56), his brother Godfrey's enemy, to retire as a monk to Monte Cassino. He enjoyed, however, the confidence of Victor II, who on Henry's death (3 Oct. 1056) reconciled Godfrey with the royal house, and next summer had Frederick elected (23 May) abbot of Monte Cassino (Humbert having forced the existing one to resign), and then (14 June) promoted him (an unprecedented appointment) cardinal priest of S. Crisogono.
In his brief reign Stephen gave an impetus to reform. At Monte Cassino, where he remained abbot, he tried to restore the rule of poverty. He opened up a wider role for Peter Damian, propagandist of reform (1007–72), by making him, in spite of his protests, cardinal bishop of Ostia. Humbert of Silva Candida, whose view that episcopal appointments should be free of lay interference he probably shared, was his chancellor and also librarian, and Hildebrand a close adviser. He frequently denounced clerical marriage and marriage within the forbidden degrees; and in summer 1057 he showed interest in the Patarenes (Pataria), a revolutionary reformist movement at Milan hostile to simony and clerical unchastity, sending Hildebrand to investigate its adherents. In spring 1058, reviving Leo IX's policies, he was planning a campaign against the Normans in south Italy, to be financed out of the treasure of Monte Cassino, which he ordered to be brought to Rome, and seems to have considered crowning Duke Godfrey as emperor so as to enlist his support; he also proposed sending envoys to Constantinople to negotiate an alliance against the common foe. In Mar. he travelled to Florence to consult Godfrey about the enterprise, died there, and was buried in S. Reparata. Being already seriously ill, he had bound the clergy and people, before leaving Rome, by a solemn oath not to elect a successor, in the event of his death, until Hildebrand returned from his mission to the German court. He probably wished to ensure that a pope would be chosen who would continue the work of reform.