Armenian Church is an independent, self-governing, autocephalous church - it has its own head, the Catholicos, not subordinate to the hierarchies of other churches. The origin of Armenian Church dates back to the period of apostolic evangelization. Armenian Church is founded by two of Christ's disciples - the Apostles Thaddeus and Bartholomew. For this reason it is called Armenian Apostolic Church.

The story goes, that Armenian king Abgar, reigning in Edessia, sends a letter to Christ, asking Him to go to Edessia to treat his incurable disease and abide in Edessia free from Hebrew oppression. Christ reply replies him, saying He wouldn't go, but "Blessed is he, who has faith in me not seeing me! As soon as I fulfill my Father's will, I will send my pupils to your country to cure both you and all your people". After Christ's Resurrection Apostle Thaddeus comes to Edessia, cures king Abgar, and, christening him and his people, becomes the bishop of Edessia. It is Apostle Thaddeus, to whom bringing to Armenia of St. Geghard (the spearhead, with which the Roman soldier lanced Christ) is inscribed. Curing the king, Thaddeus comes to Armenia, where Sanatruk reigned those days, and starts preaching throughout the country. He brings many people to faith, Sanatruk's daughter, Sandukht among them. Sanatruk starts oppressions against the faithful, Sandukht and all the faithful die. Thaddeus passes too.

The Apostle Bartholomew preaches in various strata, for the members of the Royal Family too. But as a result of the oppressions, he, Sanatruk's sister Voguhi, and many of the king's servitors die.

The full and official conversion of Armenians to Christianity was executed in 301 by St.Grigor the Enlightener in the times of Tiridates III. In 287 with support of Roman army Tiridates comes to Armenia to regain the throne of his ancestors. Grigor joins Tiridates, becoming one of his devoted comrade-in-arms. Regaining the throne, Tiridates orders Grigor to worship idols, Grigor refuses, as he has Christian faith. Tiridates tries to get Grigor do his will, but the latter keeps steady in his faith. This time Tiridates is informed, that Grigor is the son to Anak, who killed Tiridates's father, Khosrov. Learning this, Tiridates orders to throw Grigor into a deep pit (Khor Virap). Grigor, staying in the pit full of snakes and scorpions for 13-14 years, survived due to his prayers and deep faith.

Escaping oppressions of Roman emperor Diokletianus, a group of faithful virgins, beautiful Hripsimeh among them, run to Armenia, finding abode in Vagharshapat. Diokletianus sends a letter to Tiridates, asking him to find Hripsime and return her back. Soon Hripsime is brought to Tiridates. The king, struck with her beauty, asks her to marry him, but Hripsime, devoted to her faith, refuses his offer. By the kings order the servants kill Hripsime and all the virgins. Because of Hripsime's loss Tiridates, undergoing terrible emotional disturbance, gets a strange unknown disease. According to historian Agatangeghos's words, he "flew into rage, began to eat himself, and getting out of human shape, as the Babylonian king Nabuchodonosor (Nebuchadnezzar), in the shape of wild swine, like one of them went to live with them". Tiridates's sister, Khosrovidukht, sees a dream, that Grigor, who is in the deep pit, could cure the king. Nobody believes this dream, as no human being could survive in the pit for so many years, but people are sent to the pit, and Grigor is taken out and brought to Vagharshapat. The Armenian king with entire Royal House comes before Grigor and asks for remittal. After a five-day fasting (called Arajavorats Fast and kept by Armenian Church to our days) he preaches New and Old Testament for sixty days. Then Grigor goes around the country, destroying Armenian Pagan temples, in the places of which Christian Churches rise later. Inspired by the vision of the Only Begotten Son, Christ, descending to the town of Vagharshapat with a golden hammer in hand and showing the site of the first Christian church to St.Grigor the Enlightener, the latter founds in 301 AD the present-day Mother Church, the Holly Echmiatsin, which has since become the hierarchical center of Armenian Church.

In 302 Grigor the Enlightener was proclaimed the first Patriarch and Catholicos of all Armenians and later was sainted.

The spreading of Christianity faced obstacles, as Armenians did not have their own alphabet, and all the pious literature was in Greek and Assyrian, which made understanding of religion difficult for commonality. To overcome this problem, Mesrob Mashtots, a scientist, soldier and monk, invented Armenian alphabet in 405 with support of Catholicos Sahak Partev and King Vramshapuh. The first phrase, written by letters of Armenian alphabet, was "To learn wisdom and exhortation, to understand sayings reason", taken from "Book of proverbs of Solomon". Soon Sahak and Mesrop realised translation of the Bible, which for its accuracy, briefness and expressiveness received the name of "the queen of translations". Besides this, important works by Fathers of Church were translated.

Armenian Church teaches that Christ became a real and perfect Man in body, mind, and soul, without ever ceasing to be God. Christ is one person, completely human and completely divine. For Armenian Church, the nature of Christ, the God incarnate is beyond human understanding, and this potentially contradictory statement is a divine mystery.

Of Seven Ecumenical Councils Armenian Church has accepted decisions of the first three (Nicaea in 325, Constantinople in 381, Ephesus in 431), rejected the fourth and pronounced no relation to last three. Armenian Church accepts the infallibility of the Church in the Ecumenical Councils.

In 2001 all the Christian World together with Armenia celebrated 1700-th Anniversary of Adoption of Christianity in Armenia as a State Religion.