Pope, was born at Cedelle, in Sicily, in the early part of the 7th century. He became first canon regular, then cardinal priest, and finally pope, as successor of Agatho. Although his predecessor had died in January of the same year, he was installed as late as August, 682, by the emperor Constantine V, as "the most holy and blessed archbishop of old Rome, and universal pope." The reasons of this delay are unknown. Soon after his election Constantine requested him to send to Constantinople an ambassador, with full authority to decide at once on all questions of dogmas and canons, and other ecclesiastical interests. But Leo, perceiving the aim of the request, sent only a sub-deacon, who would not act in matters of any importance without first consulting with Rome. He also immediately assembled a synod to approve of the acts of the sixth oecumenical council held at Constantinople in 681, which had been brought to Rome by the legates of Agatho. In 683 he sent a legate to Constantine, with a letter anathematizing the heresy of the Monothelites, and also pope Honorius (625-638), "who, instead of purifying the Apostolic Church by the doctrines of the apostles, has come near overthrowing the faith by his treason" (Labbe, Conc. 6:1246). Leo sought to induce all the churches to accept the decisions of that council, and for that purpose translated them from Greek into Latin, sending a copy of them in the latter language to the Spanish bishops. He appears also to have given his ambassador four letters, somewhat similar as to their contents (see Mansi, 11:1050-1058), addressed to the bishops of Ostrogothia, count Simplicius, king Erwig, and the metropolitan bishop Quiricus of Toledo, expressing his wish that all the bishops of Spain would endorse the acts of the Council of Constantinople. In these letters he says: "Honorius has falsified the inviolable rule of apostolic succession which he had received from his predecessors." Baronius, wishing to rehabilitate Leo, denies the authenticity of these letters, while Pagi attempts to uphold it; Gfrörer (Kirchengesch. vol. 3, pt. 1, p. 397 sq.) also maintains their genuineness, and adduces in proof of it their corresponding precisely with the decisions of the fourteenth Council of Toledo. Leo also obtained from Constantine a promise that after the death of the titular archbishop of Ravenna his successors should, according to an old custom fallen into disuse, come to Rome to be consecrated. In exchange for this concession, Leo relieved the see of Ravenna from the obligation of paying the taxes formerly levied on the occasion of such consecration. Leo was a great friend of Church music, and did much towards improving the Gregorian chant. He built a church to St. Paul, and is said to have originated the custom of sprinkling the people with holy water. He died in July, 683: the exact date is not ascertained, and the Roman Catholic Church commemorates him on the 28th of June. See Dupin, Biblioth. des Auteurs Eccles. 5:105; Platina, Historia delle Vite dei Sommni Pontusci; Ciaconius, Vitae Res gestce Pontificum Romanorum (Romans 1677, 4 vols. folio), 1:478; Herzog, Real-Encyklop. 8:311; Hoefer, Nouv. Biog. Generale, 30:708; laxmann, Politik der Papste, 1:185;
Bower, History of the Popes, 3:134 sq.; Riddle, Hist. of the Papacy, 1:300.