Theophylact (son of Michael I)
|Co-emperor of the Byzantine Empire|
Gold solidus of Michael I, with Theophylact on the reverse
|Reign||25 December 811 – 11 July 813 (alongside Michael I Rhangabe)|
|Predecessor||Michael I Rangabe|
|Successor||Leo V the Armenian|
|Died||15 January 849|
|Father||Michael I Rangabe|
|with Staurakios as co-emperor, 803–811|
|with Theophylact as co-emperor, 811–813|
| Preceded by
| Followed by|
Leo V and the Amorian dynasty
Theophylact or Theophylaktos (Greek: Θεοφύλακτος) was the eldest son of the Byzantine emperor Michael I Rhangabe (r. 811–813) and grandson, on his mother's side, of Nikephoros I (r. 802–811). He was junior co-emperor alongside his father for the duration of the latter's reign, and was tonsured, castrated, and exiled to Plate Island after his overthrow.
Theophylact was born to Michael Rhangabe and Prokopia circa 793. He was the couple's second child after his sister Gorgo, and was named after his paternal grandfather, the droungarios of the Dodekanesos Theophylact Rhangabe, who had participated in a failed conspiracy to wrest the throne from Empress-regent Irene of Athens in 780. His maternal grandfather, Nikephoros Ι, was a staunch supporter of Irene and would soon rise to become her General Logothete (finance minister), eventually to depose her in October 802.
Following the death of Nikephoros Ι in the Battle of Pliska on 26 July 811 and the crippling of his only son and heir Staurakios in the same battle, on 2 October the court acclaimed Nikephoros's son-in-law Michael Rhangabe as emperor and forced Staurakios to abdicate. Michael immediately set about to consolidate his rule, distributing lavish gifts, crowning his wife as Augusta on 12 October, and finally, raising Theophylact – then aged eighteen – to the position of co-emperor on Christmas Day, 25 December 811. At about the same time, Michael sent an embassy under Bishop Michael of Synnada to the Frankish court, which among other issues raised the prospect of an imperial marriage between Theophylact and one of Charlemagne's daughters. Despite a warm reception at Aachen, however, Charlemagne hesitated to agree to such a match.
Nothing further is known of Theophylact until 11 July 813, when Michael, faced with a military revolt under Leo the Armenian, abdicated. The deposed imperial family was exiled to the Princes' Islands, where they were ordained as monks and nuns. Theophylact, who like his brother Nicetas was also castrated to make them incapable of claiming the throne in the future, adopted the monastic name Eustratius. He died five years after his father, on 15 January 849, and was buried alongside him in a church on Plate Island.
- Treadgold, Warren T. (1988). The Byzantine Revival, 780–842. Stanford, California: Stanford University Press. ISBN 0-8047-1896-2.
- Winkelmann, Friedhelm; Lilie, Ralph-Johannes; Ludwig, Claudia; Pratsch, Thomas; Rochow, Ilse; Zielke, Beate (2001). "Theophylaktos (#8336)". Prosopographie der mittelbyzantinischen Zeit: I. Abteilung (641–867), 4. Band: Platon (#6266) – Theophylaktos (#8345) (in German). Berlin, Germany and New York, New York: Walter de Gruyter. pp. 684–685. ISBN 978-3-11-016674-3.