Sisinnios 21 was bishop of Syke in Isauria; in 787 he attended the Second Council of Nikaia (the Seventh Ecumenical Council) and was probably present at all eight sessions, from 24 September to 23 November 787: Mansi XII 999-XIII 486. In the lists of those present at the first and seventh sessions he is styled Σισιννίου ἐπισκόπου Συκῆς: Mansi XII 999, XIII 373 (Συκίων). Elsewhere he is styled Σίσιννιος ὁ ὁσιώτατος ἐπίσκοπος Συκῆς or similar: Mansi XII 1110, XIII 149. On his bishopric, see Ramsay, Historical Geography, p. 381. At the second session he supported the traditional veneration of icons as described in statements from pope Hadrian I (Hadrianos 1) and condemned iconoclasts: Mansi XII 1110. At the fourth session he subscribed the statements read out from the Fathers in support of the veneration of icons: Mansi XIII 149. His name is missing from the list of those who subscribed the statement of the faith adopted by the Council at the seventh session, but he attended the session and the omission is perhaps a textual error.

(Publishable link for this person: )