See of Nicaea

The Metropolis of Nicaea (Greek: Μητρόπολις Νικαίας), was an ecclesiastical province (since the mid-4th century a metropolitan bishopric) of the Patriarchate of Constantinople in the city of Nicaea in the province of Bithynia (now Iznik in Turkey). A prestigious see due to its proximity to the Byzantine capital, Constantinople, and the location of two Ecumenical Councils in 325 and 787, the metropolitan see of Nicaea remained important until its conquest by the Ottoman Turks in 1331. The Christian element in the diocese diminished rapidly after that, with the flight of the Greek population and the Islamization of the remainder. As a result, the seat of the diocese was moved to Cius. The metropolis remained active until the population exchange between Greece and Turkey in the early 1920s. It remains a titular see of the Patriarchate of Constantinople as well as being, since the mid-15th century, a titular archbishopric of the Roman Catholic Church.

Nicaea was an important and prosperous city in Late Antiquity, and its local church flourished as a result. The First Ecumenical Council was held in the city in 325, and under Emperor Valens (r. 364–378), the local see was removed from the purview of its neighbour and rival, Nicomedia, and raised to the status of a separate metropolis. In the fifth century it took three suffragans from the jurisdiction of Nicomedia, and later six. In 787 a second Ecumenical Council (the Seventh) was held there, ending the first period of Byzantine Iconoclasm. In the Notitiae Episcopatuum from the 8th to the 15th centuries, Nicaea steadily occupies the eighth place in the metropolitan sees subject to the Patriarchate of Constantinople.

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