John Komnenos Angelos Doukas Synadenos (Greek: Ἰωάννης Κομνηνός Ἄγγελος Δούκας Συναδηνός) was a Byzantine noble and military leader with the rank of megas stratopedarches during the reigns of Michael VIII Palaiologos (r. 1259–1282) and Andronikos II Palaiologos (r. 1282–1328).

Synadenos appears in 1276/1277, when, along with the megas konostaulos Michael Kaballarios, he led an army against the independent ruler of Thessaly, John I Doukas. The Byzantine army was routed at the Battle of Pharsalus, and Synadenos himself was captured, while Kaballarios was killed whilst trying to escape.^[1][2][3] He was released or ransomed from captivity, and in 1281 he participated in the campaign against the Angevins in Albania which led to the Byzantine victory at Berat.^[3][4] Finally, in 1283, he participated in another campaign against John Doukas, under Michael Tarchaneiotes.^[2][3]

Eventually, Synadenos retired to a monastery with the monastic name Joachim. After his death (sometime between 1310 and 1328), his wife, Theodora Palaiologina, the daughter of Constantine Palaiologos, the half-brother of Michael VIII, became a nun with the name Theodoule, and founded the Convent of the Mother of God Bebaia Elpis ("Certain Hope") in Constantinople. The convent's typikon (the so-called "Lincoln College typikon"), authored largely by Theodora, includes lavish depictions of the family's members.^[2][5][6]

With Theodora, John had four children, who were reportedly all young when he died:^[2][6]

• John Synadenos, megas konostaulos.^[6][7]
• Euphrosyne Synadene, who was pledged to become a nun since infancy, and was the second founder of the Bebaia Elpis along with her mother.^[8][9]
• An unnamed daughter, once reportedly considered as a possible bride for the Bulgarian tsar Theodore Svetoslav.^[3]
• Theodore Synadenos, protostrator, he played a major role in the Byzantine civil wars of the first half of the 14th century.^[10][11]

• Geanakoplos, Deno John (1959). Emperor Michael Palaeologus and the West, 1258–1282: A Study in Byzantine-Latin Relations. Cambridge, Massachusetts: Harvard University Press. OCLC 1011763434.
• Guilland, Rodolphe (1967). Recherches sur les institutions byzantines [Studies on the Byzantine Institutions]. Berliner byzantinische Arbeiten 35 (in French). Vol. 1. Berlin and Amsterdam: Akademie-Verlag & Adolf M. Hakkert. OCLC 878894516.
• Kazhdan, Alexander, ed. (1991). The Oxford Dictionary of Byzantium. Oxford and New York: Oxford University Press. ISBN 0-19-504652-8.
• Polemis, Demetrios I. (1968). The Doukai: A Contribution to Byzantine Prosopography. London: The Athlone Press. OCLC 299868377.