SISINNIO I, saint. — Archbishop of Constantinople, died 24 December 427. Initially a priest in the suburb of Elia, on 28 February 426 he was elected to the Byzantine see instead of Filippo di Side and Proclo, whom he subsequently appointed bishop of Cyzicus.
S. condemned the sect of the Messalians and was, according to the testimony of his contemporary, Pope Celestine, a simple man faithful to Catholic doctrine. His feast is celebrated by the Greeks on 11 October.
BIBL.: Acta SS. Octobris, V, Parigi 1869, pp. 627–629; Fliche-Martin - Frutaz, IV, pp. 158–159. Ignazio Ortiz de Urbina