The Catholicos of All Armenians (plural Catholicoi, due to its Greek origin) is the Chief bishop of Armenia's national church, the Armenian Apostolic Church. It is one of the Oriental Orthodox churches that do not accept the decisions of the Council of Chalcedon. The first Catholicos of All Armenians was Saint Gregory the Illuminator. It were apostles Saint Thaddeus and Saint Bartholomew, who brought Christianity to Armenia in the 1st century.

The Supreme Spiritual and Administrative leader of the Armenian Church is the Supreme Patriarch and Catholicos of All Armenians, who is the worldwide spiritual leader of the Nation, for Armenians both in Armenia and dispersed throughout the world. He is Chief Shepherd and Pontiff to the Armenian faithful. The spiritual and administrative headquarters of the Armenian Church, the , located in the city of Vagharshapat, Republic of Armenia, was established in 301 AD

See also

• List of Catholicoi of Armenia
• Catholicos of Cilicia