Eustathius the Confessor was a 9th-century bishop of Kios, an ancient city in the Roman province of Bithynia in northwest Asia Minor, located at present-day Gemlik, Turkey, on the Sea of Marmara. The Orthodox Church in America's synaxarion also identifies him under the broader title 'Bishop of Bithynia.'
Before his episcopate he was a monk, remembered as meek, wise, and pious, filled with great faith and love for his neighbor. He was raised to the episcopal throne on account of his virtuous conduct, and for many years guided his flock by his example of virtuous life.
During the period of Byzantine Iconoclasm he openly opposed the heretics and defended the veneration of holy icons. Reported to the emperor, he was imprisoned, severely beaten, removed from his see, and sent into exile, where he died after three years of insults, deprivation, hunger, and want. His feast day is March 29.