Greek Orthodox Church can refer to any of several hierarchical churches within the larger group of mutually recognizing Eastern Orthodox churches:

• the Orthodox Church of Constantinople, headed by the Patriarch of Constantinople, who is also the "first among equals" of the Eastern Orthodox Communion.
• the Church of Greece, which has been autocephalous since 1833.
• any Eastern Orthodox church that uses a Greek liturgy, including the Orthodox Churches of Alexandria, Antioch, Jerusalem, and Cyprus. These churches are members of the Eastern Orthodox Communion and therefore in full communion with each other. Greek Orthodox churches in the Americas and Australia are subject to the Constantinopolitan hierarchy. These should not be confused with the Slavic-rite Orthodox Church in America, which is one of the 16 autocephalous Eastern Orthodox churches, having been granted autocephaly in 1970 by the Patriarch of Moscow. This status is not recognized by the Ecumenical Patriarch nor by some of the other autocephalous Churches.