Feast of Orthodoxy

The Feast of Orthodoxy (or Sunday of Orthodoxy or Triumph of Orthodoxy) is celebrated on the first Sunday of Great Lent in the Eastern Orthodox Church and other churches using the Byzantine Rite to commemorate, originally, only the final defeat of iconoclasm[1] on the first Sunday of Lent in 843, and later also opposition to all heterodoxy.[2]

Late 14th-early 15th century icon illustrating the "Triumph of Orthodoxy" under the Byzantine Empress Theodora and her son Michael III over iconoclasm in 843. (National Icon Collection 18, British Museum)