Pope Benedict X (reigned 1058-1059; died c. 1073 or 1080), was born John Minicus, and later became Cardinal Bishop of Velletri. He was elected in 1058, his election having been arranged by the Count of Tusculum. However, a number of Cardinals alleged that the election was irregular, and that votes had been bought; these cardinals were forced to flee Rome. Hildebrand, later Pope Gregory VII, had been sent by the late Pope Stephen X to the court of Empress Agnes (mother and regent for Holy Roman Emperor Henry III, then a minor), who had questioned the validity of Stephen X's election. When, on his return to Rome, he heard of Benedict X's election, he decided to oppose it, and obtained the support of the Duke of Lorraine-Tuscany and Empress Agnes for the election of Gerhard of Burgundy, Bishop of Florence, as Pope instead. Those cardinals who had opposed Benedict X's election met at Siena in December 1058, and elected Hildebrand's candidate as Pope, who then took the name Nicholas II.
Nicholas II proceeded towards Rome, along the way holding a synod at Sutri, where he pronounced Benedict X deposed and excommunicated. The supporters of Nicholas II then gained control of Rome, and forced Benedict X to flee to the castle of Gerard of Galeria. Having arrived in Rome, Nicholas II then proceeded to wage war against Benedict X and his supporters, with Norman assistance. An initial battle was fought in Campagna in early 1059, which was not wholly successful for Nicholas II; but later that same year, his forces conquered Praeneste, Tusculum and Numentanum, and then attacked Galeria, forcing Benedict X to surrender and renounce the Papacy.
Benedict X was then allowed to go free, and he retired to one of his family estates; but Hildebrand then had him imprisoned in 1060 in the hospice of St. Agnese, where he died, still a prisoner, sometime around 1073 or 1080.
The most important consequence of the affair of Benedict X was the adoption of new laws on papal elections, at a synod hosted by Nicholas II in the Lateran Palace at Easter 1059.