Great Church

The term "Great Church" (Latin ecclesia magna) is a concept in the historiography of early Christianity describing the rapid growth and structural development of the Church in 180-313 CE (around the time of the Ante-Nicene Period) and its claim to universally represent Christianity within the Roman Empire. The term is primarily associated with the Roman Catholic account of the history of Christian theology, but is also used by non-Catholic historians.

In modern Catholic usage, the "Great Church" broadly means the majority united Catholic and Orthodox Christian church in the West continuing in authority from the Twelve Apostles to today, and all bishops who remained in fellowship with the Bishop of Rome.

The "epoch of the Great Church" is counted as beginning around the end of the 2nd century when, despite the persecution of Christians, the religion became established numerically and organizationally, eventually becoming the State church of the Roman Empire in 380. However, at the Council of Chalcedon in 451, an Oriental Orthodox branch parted ways with the Great Church due to Christological differences.

Cunningham, and separately, Kugel and Greer state that Irenaeus's statement in Against Heresies (written c. 180 CE) is the first recorded reference to the "Great Church" as the existence of a worldwide Christian church with a core set of shared beliefs. Irenaeus states:

The Church, though dispersed through the whole world, even to the ends of the earth, has received from the apostles and their disciples this faith: ... As I have already observed, the Church, having received this preaching and this faith, although scattered throughout the whole world, yet, as if occupying but one house, carefully preserves it... For the churches which have been planted in Germany do not believe or hand down anything different, nor do those in Spain, nor those in Gaul, nor those in the East, nor those in Egypt, nor those in Libya, nor those which have been established in the central regions of the world. But as the sun, that creature of God, is one and the same throughout the whole world, so also the preaching of the truth shineth everywhere, and enlightens all men that are willing to come to a knowledge of the truth.

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