The Greek Orthodox Church (Greek: Hell?northódox? Ekkl?sía) is formed by several autocephalous churches within the larger communion of Eastern Orthodox Christianity whose liturgy is traditionally conducted in Koine Greek, the original language of the New Testament, and whose clergy is completely or predominantly ethnically Greek or was for a large part of its history, such as in the case of Antioch, which was fully placed under non-Greek control only in 1899.

Included are four ancient Eastern Orthodox patriarchates:

• the Great Church of Christ in Constantinople http://www.ec-patr.org/, headed by the Ecumenical Patriarch of Constantinople, who is also the "first among equals" of the Eastern Orthodox Communion,
• the Greek Orthodox Church of Alexandria http://www.greekorthodox-alexandria.org/index.php?lang=en,
• the Greek Orthodox Church of Antioch http://www.antiochpat.org/english/sitefiles/,
• the Greek Orthodox Church of Jerusalem http://www.jerusalempatriarchate.org/ ^{(in Greek and Arabic)};

two national autocephalous churches:

• the Orthodox Church of Greece http://www.ecclesia.gr/English/EnIndex.html,
• the Orthodox Church of Cyprus http://www.churchofcyprus.org.cy/ ^{(in Greek)};

as well as

• the Orthodox Church of Mount Sinai http://www.sinaimonastery.com/.

The Greek Orthodox Archdiocese of America http://www.goarch.org/ and the Greek Orthodox Archdiocese of Australia http://www.greekorthodox.org.au/general/ are both eparchies of the Ecumenical Patriarchate of Constantinople.

Note: The Greek Orthodox Archdiocese of America should not be confused with the autocephalous Russian Orthodox Church in America whose autocephaly ? granted by the Patriarchate of Moscow ? is not recognized by Constantinople and many other churches of the Eastern Communion due to political reasons.

de:Griechisch-orthodoxe Kirche nl:Grieks-orthodoxe Kerk it:Chiesa greco-ortodossa pt:Igreja Ortodoxa Grega

The Greek Orthodox Bible has 50 books in its Old Testament.