John of Constantinople (died 839) was an abbot of the Cathares Monastery, in

Constantinople la, Constantinopolis ota, قسطنطينيه , alternate_name = Byzantion (earlier Greek name), Nova Roma ("New Rome"), Miklagard/Miklagarth (Old Norse), Tsargrad ( Slavic), Qustantiniya (Arabic), Basileuousa ("Queen of Cities"), Megalopolis (" ...

. He clashed with Emperor

Leo the Armenian Leo V the Armenian ( gr, Λέων ὁ ἐξ Ἀρμενίας, ''Leōn ho ex Armenias''; 775 – 25 December 820) was the Byzantine emperor from 813 to 820. A senior general, he forced his predecessor, Michael I Rangabe, to abdicate and assumed ...

, who was instituting a policy of

iconoclasm Iconoclasm (from Ancient Greek, Greek: grc, wikt:εἰκών, εἰκών, lit=figure, icon, translit=eikṓn, label=none + grc, wikt:κλάω, κλάω, lit=to break, translit=kláō, label=none)From grc, wikt:εἰκών, εἰκών + wi ...

. John survived torture. He is considered a saint by the

Catholic The Catholic Church, also known as the Roman Catholic Church, is the largest Christian church, with 1.3 billion baptized Catholics worldwide . It is among the world's oldest and largest international institutions, and has played a ...

and

Eastern Orthodox Eastern Orthodoxy, also known as Eastern Orthodox Christianity, is one of the three main branches of Chalcedonian Christianity, alongside Catholicism and Protestantism. Like the Pentarchy of the first millennium, the mainstream (or "canonical") ...

churches, and is celebrated by them respectively on April 18 and

April 27 Events Pre-1600 * 247 – Philip the Arab marks the millennium of Rome with a celebration of the ''ludi saeculares''. * 395 – Emperor Arcadius marries Aelia Eudoxia, daughter of the Frankish general Flavius Bauto. She becomes one of ...

.
Ὁ Ὅσιος Ἰωάννης ὁ Ὁμολογητής
'' 27 Απριλίου. ΜΕΓΑΣ ΣΥΝΑΞΑΡΙΣΤΗΣ.

References

813 deaths 9th-century Christian saints 9th-century Byzantine monks Byzantine Iconoclasm Year of birth unknown {{Byzantine-bio-stub