Leo, the name of 13 Popes of Rome, of which the following are the chief: - Leo I., called "the Great," born towards the end of the 4th century, probably at Rome. In 440, when mediating between Aetius and Albinus in Gaul, he was elected Pope, and occupied the Papal throne till his death in 461. When Attila invaded Italy in 452 Leopersuaded him to turn back, and four years later induced Genseric the Vandal to moderate the outrages of his troops when they took Rome.
Leo III., Pope from 795 to 816. In 799 an attempt made to depose him by the nephews of his predecessor, Adrian I., compelled him to flee to Spoleto, and subsequently to invoke the aid of Charlemagne. The latter, having acted as a judge in the case, acquitted him, and while the Frank Emperor lived Leo was at peace. A year after the trial, in 800, Charlemagne was crowned by the Pope at Rome, and the Holy Roman Empire was founded. Leo, however, contested with his successor the temporal sovereignty of Rome. Leo X. (Giovanni de' Medici), born at Florence in 1475. In 1513, when his family were restored to Florence, he was elected Pope. He defeated a French invasion at the outset of his pontificate by the employment of Swiss troops, but after the battle of Marignano (1515) was obliged to submit to the loss of Parma and Piacenza. He took sides with Charles V. against Francis I., and on the expulsion of the French from Milan in 1521 recovered the lost duchies. He bad also gained possession of Urbino, and had further magnificent projects in view when he died suddenly, it was thought by some, of poison. Leo XIII. He acquired great distinction in many departments of knowledge, inotably in philosophy, and in his later years became distinguished as a Latin poet. He was appointed in 1837 Referendary of the Segnatura, and while apostolic delegate at Benevento in the succeeding years he put down brigandage with a high hand. At the close of 1873 he became a cardinal, and in the later years of Pius IX. exercised a predominant control in matters of Papal policy. In 1877 he was appointed "Cardinal Camerlengo of the Holy Roman Church," and in the following year was chosen as successor to Pius IX. in the Papal chair. He reversed the ultramontane policy of the latter, and greatly improved the relations of the Papacy with Germany and France, being chosen as arbitrator in a dispute between Spain and the former in 1885, and in 1892 giving his sanction to the Republican Government. He declined to recognise the Italian Government in Rome, refused the vote of an income, and frequently protested against the law of guarantees and all forms of liberal education. At the same time he put forward the claims of the Papacy to intervene in the Socialistic question, and supported Lavigerie in his crusade against African slavery.