Ecumenical Patriarchate of Constantinople

The Ecumenical Patriarchate of Constantinople is one of the fifteen to seventeen autocephalous churches that together compose the Eastern Orthodox Church. It is headed by the Ecumenical Patriarch of Constantinople.

Because of its historical location as the capital of the former Eastern Roman Empire and its role as the mother church of most modern Orthodox churches, Constantinople holds a special place of honor within Orthodoxy and serves as the seat for the Ecumenical Patriarch, who enjoys the status of primus inter pares among the world's Eastern Orthodox prelates and is regarded as the representative and spiritual leader of Eastern Orthodox Christians.

Source: Wikipedia