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Main communion

The Eastern Orthodox Church is a communion of 15 autocephalous —that is, administratively completely independent—regional churches, plus the Orthodox Church in America and two Ukrainian Orthodox Churches. The Orthodox Church in America is recognised as autocephalous only by the Russian, Bulgarian, Georgian, Polish and Czech-Slovak churches. In December 2018, representatives of two unrecognised Ukrainian Orthodox churches, along with two metropolitans of the recognised, but self-declared autocephalous Ukrainian Orthodox Church of the Moscow Patriarchate, proclaimed the formation of the unified Orthodox Church of Ukraine. On 5 January 2019, the Orthodox Church of Ukraine received its tomos of autocephaly (decree which defines the conditions of a church's independence) from the Ecumenical Patriarchate and thus received a place in the diptych.

Each church has defined geographical boundaries of its jurisdiction and is ruled by its council of bishops or synod presided by a senior bishop–its primate (or first hierarch). The primate may carry the honorary title of patriarch, metropolitan (in the Slavic tradition) or archbishop (in the Greek tradition).

Each regional church consists of constituent eparchies (or dioceses) ruled by a bishop. Some churches have given an eparchy or group of eparchies varying degrees of autonomy (self-government). Such autonomous churches maintain varying levels of dependence on their mother church, usually defined in a tomos or other document of autonomy.

Below is a list of the 15 autocephalous Orthodox churches forming the main body of Orthodox Christianity, all of which are titled equal to each other, but the Ecumenical Patriarchate is titled the first among equals. Based on the definitions, the list is in the order of precedence and alphabetical order where necessary, with some of their constituent autonomous churches and exarchates listed as well. The liturgical title of the primate is in italics.

Within the main body of Eastern Orthodoxy there are unresolved internal issues as to the autonomous or autocephalous status or legitimacy of the following Orthodox churches, particularly between those stemming from the Russian Orthodox or Constantinopolitan churches: