Mostly Christians since the early fourth century A.D., the Armenians claim to represent the first state to adopt Christianity as an official religion. The independent Armenian church considers its founders to have been the apostles Bartholomew and Thaddeus and officially calls itself the Armenian Apostolic Church. (It is also referred to as the Armenian Orthodox Church or the Gregorian Church.) The conversion of Armenia by Saint Gregory the Illuminator occurred by about A.D. 314, although the traditional date is A.D. 306. Armenian Christians then remained under the powerful combined religious and political jurisdiction of the Byzantine Empire until the sixth century. At that point, the Armenian church asserted its independence by breaking with the Byzantine doctrine of Christ's dual (divine and earthly) nature, which had been expressed officially by the Council of Chalcedon in A.D. 451.

Since the schism, the Armenian Apostolic Church has been in communion only with the monophysite churches (those believing that the human and divine natures of Christ constitute a unity) of Egypt, Syria, and Ethiopia. Rather than embrace the monophysite doctrine, however, the Armenian church holds that Christ had both a divine and a human nature, inseparably combined in a complete humanity that was animated by a rational soul. The Armenian church also rejects the juridical authority of the pope and the doctrine of purgatory.

Although the Armenian Apostolic Church often is identified with the Eastern Orthodox churches of Eastern Europe, Russia, and Georgia, the Armenian church has been juridically and theologically independent since the early Middle Ages. As a national church, it has played a vital role in maintaining Armenian culture, through the preservation and expansion of written traditions and as a cultural focus for Armenians scattered around the world. In the long periods when Armenians did not have a state of their own, their church was both a political and a spiritual leader, and religion was at the center of the Armenian national self-image. Under the millet system by which the Ottoman Empire ruled subject peoples, the patriarch of Constantinople was recognized as the head of the Armenian community, and the Russian tsarist empire treated the catholicos, the titular head of the Armenian Apostolic Church, as the most important representative of the Armenian people.

The Armenian Apostolic Church is headed by Vazgen I, supreme catholicos of all Armenians, who resides in the holy city of Echmiadzin, west of Erevan. The membership of the church is split between a majority that recognizes the supreme catholicos without qualification and a minority that recognizes the catholicos of Cilicia, whose seat is at Antilyas in Lebanon. Closely affiliated with the Armenian Revolutionary Federation (ARF), the minority branch of the church was hostile to any accommodation with communist regimes while Armenia was under Soviet rule. Both branches of the church have been closely identified with the movement for national independence, however. A split occurred within the United States membership of the Ar7ee Armenian Apostolic Church in 1933, when ARF sympathizers assassinated the Armenian archbishop of New York. Two factions remained distinct in the United States in the early 1990s.

Two additional patriarchates in Jerusalem and Istanbul lack the status of full catholicates. Three dioceses are located in other former Soviet republics, and twenty bishoprics function in other countries. Total church membership was estimated at 4 million in 1993. The Armenian Orthodox Academy and one seminary provide religious training.

About 94 percent of the population of Armenia belongs to the Armenian Apostolic Church. Small Roman Catholic and Protestant communities also exist in Armenia. Catholic missionaries began converting Armenians in the Ottoman and Persian empires in the early modern era, and American Protestant missionaries were active in the nineteenth century. The Kurdish population, which totaled 56,000 in 1993, is mostly Muslim but also includes many Christians. Kurds now constitute the largest Muslim group in Armenia because most Azerbaijani Muslim emigrated in the early 1990s. A Russian Orthodox community also exists.

Data as of March 1994