Michael I Rangabe (also spelled Rhangabe; Greek: Μιχαὴλ Αʹ Ῥαγκαβές, romanized: Mikhaḗl 1 Rhangkabés; c. 770 – 11 January 844) was Byzantine emperor from 811 to 813. A courtier of Emperor Nikephoros I (r. 802–811), he survived the disastrous campaign against the Bulgars and was preferred as imperial successor over Staurakios (r. 811–811), who was severely injured. He was proclaimed emperor by Patriarch Nicephorus I of Constantinople on 2 October 811.
Michael's policies were generally conciliatory, and he was overwhelmingly influenced by the iconodule clerics Nikephoros and Theodore the Stoudite. He improved relations with the Franks, even to the point of recognising Charlemagne as an emperor – although not "of the Romans" – and requesting papal arbitration in the Moechian controversy. His half-hearted leadership of the campaign against the Bulgars resulted in defeat in the Battle of Versinikia. The stratēgos of the Anatolic Theme, Leo the Armenian, a popular and successful general, abandoned Michael on the battlefield but was proclaimed emperor by the military, in what was the last military overthrow of an emperor in Byzantine history. Michael was pressured to abdicate, and he retired to a monastery. His sons were castrated to prevent the continuation of his dynasty.
