Agatho 9 | Prosopography of the Byzantine Empire |
| Sex | M |
| Floruit | M IX |
| Dates | 855 (taq) / 855 (tpq) |
| Religion | Christian |
| Locations | Tuder (Tuscia) (officeplace); Tuder (Tuscia); Rome; St Leucius (Basilica of, Rome) |
| Occupation | Bishop |
| Titles | Bishop, Tuder (Tuscia) (office) |
| Textual Sources | Liber Pontificalis, ed. L. Duchesne, Le liber pontificalis. Texte, introduction et commentaire, 2 vols. (Paris, 1886-92); re-issued with 3rd vol. by C. Vogel, (Paris, 1955-57) (chronicle) |
Agatho 9 was bishop of Tuder (Todi) (in Umbria); in 855, after the election of Benedict (Benediktos 7) as bishop of Rome, Agatho secretly left Rome, with the bishop of Portus, Radoald 1, to join the supporters of the rival claimant to be pope, Anastasius (Anastasios 25), at the Basilica of St Leucius (five miles from Rome): Lib. Pont. 106. 9.
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