The Armenian Apostolic Church (Armenian: Հայաստանեայց Առաքելական Եկեղեցի, Hayastaneayc' Aṙak'elakan Ekeġec'i) is the world's oldest National Church and is one of the most ancient Christian communities. Armenia was the first country to adopt Christianity as its official religion in 301 AD, in establishing this church. The Armenian Apostolic Church traces its origins to the missions of Apostles Bartholomew and Thaddeus in the 1st century.
The official name of the Church is the One Holy Universal Apostolic Orthodox Armenian Church. It is sometimes mistakenly referred to as the Gregorian Church, and this name is not acceptable by the Church, because the true name of Apostolic implies the Apostles Bartholomew and Thaddeus as the founders, and St. Gregory the Illuminator as merely the first official head of the Church.
The Armenian Apostolic Church is a branch and an integral part of the Universal Christian Church. Until the Council of Chalcedon (451 A.D.) the Christian Church was one. To set the dogmas of this one universal church, and to free it from the heretical nations infesting it in the 2nd and 3rd centuries, three Ecumenical Councils were convened: Nicea in 324, Constantinople in 381 and Ephesus in 431.
In these three Councils the Fathers of the Christian Church formulated the orthodox interpretations of the Trinitarian doctrine, the incarnation and the nature of Jesus Christ, the understanding of the Holy Spirit, the position of Virgin Mary as Theotokes (God bearing) and all other theological points. In these three Councils the theology of the Christian religion was formulated for general usage in a concise form (Nicene Creed). Furthermore, in the last of these three councils it was solemnly declared that any further change, addition or deletion from the Creed or the accepted dogmas should be considered heresy.
The Armenian Apostolic Church accepted and has since strongly adhered to these dogmas and has never deviated from the doctrine set forth in the first three ecumenical councils. Other Churches have seen fit to call additional Councils. The changes suggested and accepted in these additional Councils have not been accepted by the Armenian Apostolic Church which has faithfully and firmly stood on the teachings of the first three councils, as have other Churches, namely the Oriental Orthodox churches.
The Armenian Church today is an autocephalous body, The Church is unique in that besides being a religious institution it is also a national institution inasmuch as almost all of its members are either Armenians or of Armenian descent, and for many centuries has played, in the absence of organized Armenian government, the role of this latter.