Eastern Orthodoxy by country
Based on the numbers of adherents, the Eastern Orthodox Church (also known as Eastern Orthodoxy) is the second largest Christian communion in the world after the Roman Catholic Church. The most common estimates of the number of Eastern Orthodox Christians worldwide is approximately 200–260 million. The numerous Protestant groups in the world, if taken all together, outnumber the Eastern Orthodox, but they differ theologically and do not form a single communion.
Eastern Orthodox Church
Below is a list of the 14 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 and/or legitimacy of the following Orthodox churches, particularly between those stemming from the Russian Orthodox or Constantinopolitan churches:
True Orthodoxy separated from the mainstream communion over issues of ecumenism and calendar reform since the 1920s. The movement rejects the Ecumenical Patriarchate of Constantinople, the Moscow Patriarchate, and those churches in communion with them, accusing them of heresy and placing themselves under bishops who do the same. They adhere to the use of the old Julian calendar since antiquity, claiming that the calendar reform in 1920s is in contravention of the ecumenical councils. True Orthodox writers have argued that in missionary areas such as the United States, Orthodox (SCOBA) membership numbers may be overstated, with the comparative number of True Orthodox as up to 15% of the Orthodox population, in Russia, it has been claimed by some clergy that up to a million Russians may be True Orthodox of different jurisdictions, though the total number is often cited at 1.7–2 million together.