SISINNIUS I, St. — Archbishop of Constantinople, d. 24 Dec. 427. After serving as a priest in the suburb of Elia, he was elected to the Byzantine see on 28 Feb. 426 in place of Philip of Side and Proclus, whom he later appointed bishop of Cyzicus.
S. condemned the Messalian sect and, according to the testimony of his contemporary Pope Celestine, was a simple man faithful to Catholic doctrine. His feast is celebrated by the Greeks on 11 Oct.
BIBL.: Acta SS. Octobris, V, Paris 1869, pp. 627-29; Fliche-Martin - Frutaz, IV, pp. 158-59.