This article treats the manner in which the Eastern Orthodox Churches are organized, rather than the doctrines, traditions, practices, or other aspects of Eastern Orthodoxy.
The Eastern Orthodox Churches are a communion comprising the collective body of sixteen separate autocephalous hierarchical churches that recognize each other as "canonical" Orthodox Christian churches.
The head of the Body of Christ can only be Christ. The Eastern Churches have no one so powerful as the Roman Pope. The highest-ranking bishop of the communion is the Patriarch of Constantinople, who is also primate of one of the sixteen churches. The sixteen organizations are in full communion with each other, so any priest of any of those churches may lawfully minister to any member of any of them, and no member of any is excluded from any form of worship in any of the others. Despite the fact that, like the Roman Catholic church, they are "closed communion" churches, i.e. with rare exceptions excluding non-members from receiving the Eucharist, nonetheless they admit each other's members to that sacrament. This is completely non-paradoxical as far as the Orthodox are concerned, since, even though there may be many "Churches", there is only one Church, in Orthodox ecclesiology. That is, each "Orthodox Church" is actually a portion of the Orthodox Church as a whole. Friction among them is over matters of church politics rather than doctrine.
Like the Roman Catholic Church, the Eastern Orthodox church claims to be the One Holy Catholic and Apostolic Church.
All the disagreements among persons of differing religious beliefs beget strange nomenclature, and accordingly a church adhering to so-called Western Orthodoxy is actually a Vicariate within the Antiochian Orthodox Church (it is never called the "Western Orthodox Church" by anyone who actually worships within that Vicariate) and thus a part of the Eastern Orthodox Church as that term is defined here.
Note that Oriental Orthodoxy separated from the One Holy Catholic and Apostolic Church in the 5th century, well before the 11th century Great Schism. It should not be confused with Eastern Orthodoxy.
At the beginning of the 11th century, the One Holy Catholic and Apostolic Church was ruled by five patriarchs: those of Rome, Constantinople, Alexandria, Antioch, and Jerusalem. Each had jurisdiction over bishops in a specified geographic region. The patriarch of Rome was "first in place of honor" among the five patriarchs. Did that mean he had authority over the other four patriarchs, or was his primacy merely honorary? Disagreement about the answer to that question was one of the causes of the Great Schism in the year 1054, which split the church into the western Roman Catholic Church, headed by the Patriarch of Rome, and the Eastern Orthodox Church, led by the four eastern patriarchs. After the schism, in the Eastern Orthodox churches, the Patriarch of Constantinople has always had honorary primacy. The importance of the insistence that one patriarch does not have authority over the others is seen in the fact that these separate churches are autocephalous. Since then, the Eastern Orthodox Church has expanded and reorganized, so that today it has sixteen autocephalous churches rather than only four.
Eastern Orthodox Church jurisdictions
Churches with ambiguous status
Churches in resistance
These Churches are resistant to what they perceive as the errors of Modernism and Ecumenism in mainstream Orthodoxy, but they do not consider themselves schismatic; they do refrain from concelebration of the Divine Liturgy with the mainline Orthodox Churches while they remain fully within the canonical boundaries of the Church, i.e. maintaining Orthodox belief, legitimate episcopal succession, and communities with historical continuity. They will commune the faithful from all the canonical jurisdictions and are recognized by and in communion with the Russian Orthodox Church Outside Russia.
Churches that have voluntarily "walled themselves off"
These Churches do not practice Communion with any other Orthodox jurisdictions nor do they tend to recognize each other.
Churches that are unrecognized by others
The following Churches recognize all other mainstream Churches, but are not recognized by (m)any of them due to various disputes: