The eleventh-century papal reform transformed western European Church and society and permanently altered the relations of Church and State in the west. The reform was inaugurated by Pope Leo IX (1048/9-1054) and given a controversial change of direction by Pope Gregory VII (1073-85). This book contains the earliest biographies of Leo IX and Gregory VII, presented here for the first time in English translation with detailed commentaries. The biographers of Leo IX were inspired by his universally acknowledged sanctity, whereas the biographers of Gregory VII wrote to defend his reputation against the hostility generated by his reforming methods and his conflict with the German king Henry IV. The earliest Life of Leo IX, begun during his lifetime, was the work of an anonymous Lotharingian author, perhaps a monk of the abbey of St Evre in the diocese of Toul, where Leo had once been bishop. The papal reform movement is the principal subject of the Book to a Friend, written by Bishop Bonizo of Sutri soon after the death of Gregory VII (1085). Bonizo sought to defend Gregory against the critics who denounced him as a schismatic and warmonger. The defence of the Pope's reputation was also the purpose of the Life of Gregory VII composed by Paul of Bernried in 1128. This collection also contains an extract from the violently anti-Gregorian polemic of Bishop Benzo of Alba (1085) and the short biography of Leo IX composed in the papal curia in the 1090s by Bishop Bruno of Segni. These narrative sources bear witness to the startling impact of the papal reform and of the 'Investiture Contest', the conflict of empire and papacy that was one of its consequences.