Greek Catholic church, an Eastern Catholic church of the Byzantine rite, in communion with Rome since the mid-19th century. A small body of Greek Catholics came into existence in Constantinople (modern Istanbul) and Thrace largely through the efforts of John Hyacinth Marango, a Latin priest, and Polycarp Anastasiadis, a Greek priest. An apostolic exarchate, eventually located in Athens, was created in 1911, and a separate exarchate at Istanbul was set up in 1932.
The term Greek Catholic properly applies only to members of the Catholic church, either Byzantine or Latin rite, who are of Greek nationality, but Catholic Melchites and Ukrainians also call themselves Greek Catholics.