The Greek Orthodox churches are descended from churches which the Apostles founded in the
Balkans and the
Middle East during the first century A.D.,
[b] and they maintain many traditions practiced in the ancient Church.
 Orthodox Churches, unlike the
Catholic Church, have no Bishopric head, such as a
Pope, and hold the belief that Christ is the head of the Church. However, they are each governed by a committee of Bishops, called the Holy Synod, with one central Bishop holding the honorary title of "first among equals."
Greek Orthodox Churches are united in
communion with each other, as well as with the other
Orthodox Churches (such as the
Russian Orthodox Church). The Orthodox hold a common doctrine and a common form of worship, and they see themselves not as separate Churches but as administrative units of one single Church. They are notable for their extensive tradition of
iconography (see also:
Byzantine art), for their veneration of the
Mother of God and the
Saints, and for their use of the
Divine Liturgy on Sundays, which is a standardized worship service dating back to the fourth century A.D. in its current form. The most commonly used Divine Liturgy of the Orthodox Church was written by
Saint John Chrysostom (347–407 A.D.). Others are attributed to
St. Basil the Great,
St. James, the Brother of God and
St. Gregory the Dialogist.
The current territory of the Greek Orthodox Churches more or less covers the areas in the
Anatolia, and the
Eastern Mediterranean that used to be a part of the
Byzantine Empire. The majority of Greek Orthodox Christians live within
Greece and elsewhere in the southern
Balkans (especially in
Albania), but also in Jordan, the Occupied Palestinian territories, Iraq,
Turkey, and the
South Caucasus. In addition, due to the large Greek diaspora, there are many Greek Orthodox Christians who live in
North America and
Australia. Orthodox Christians in Finland, who compose about 1% of the population, are also under the jurisdiction of a Greek Orthodox Church (the Ecumenical Patriarchate).
There are also many Greek Orthodox Christians, with origins dating back to the
Ottoman periods, who are of
Arabic-speaking or mixed Greek and Arabic-speaking ancestry and live in southern
Egypt. They attend churches which conduct their services in
Arabic, the common language of most Greek Orthodox believers in the
Levant, while at the same time maintaining elements of the
Byzantine Greek cultural tradition.
Greeks in Russia and
Greeks in Ukraine, as well as
Pontic Greeks and
Caucasus Greeks from the former Russian
Transcaucasus, often consider themselves both Greek Orthodox and
Russian Orthodox, which is consistent with the Orthodox faith (since Orthodoxy is the same across ethnic boundaries). Thus, they may attend services held in
Old Russian and
Old Church Slavonic, without this in any way undermining their Orthodox faith or distinct Greek ethnic identity. Over the centuries, these Pontic Greek-speaking Greek Orthodox communities have mixed through intermarriage in varying degrees with ethnic Russians and other Orthodox Christians from mainly
Southern Russia, where most of them settled between the
Middle Ages and early 19th century.