The Armenian Church is an independent Christian church, also known as the Armenian Apostolic Orthodox Church. Its head is the Catholicos, who resides at Holy Etchmiadzin, near Yerevan, the capital of Armenia. 
Christianity was declared the state religion of Armenia in AD 301. Armenia thus became the first nation to adopt Christianity as a state religion. This was largely due to the efforts of St. Gregory the Illuminator. Born a nobleman, he converted Armenia's king Tiridates III, who had formerly perse-cuted the Christians. Conversion of the rest of the population soon followed. It was St. Gregory who built the Mother Church at Etchmiadzin in AD 303.
Until the 5th century, Christian worship in Armenia was conducted in Greek or Syriac, since there was no Armenian alphabet, hence no written language. In AD 404, St. Mesrob (at that time a monk) completed an alphabet of 36 letters. His objective was to translate the Bible into Armenian, and the golden age of classical Armenian literature began shortly thereafter.
Persia reduced Armenia to vassaldom and in AD 450 issued a decree ordering all Christians to embrace the Zoroastrian religion. The Armenians, under Prince Vartan Mamigonian, rose in revolt. This culminated in the Battle of Avarayr. Vartan lost the battle, but under the leadership of his nephew, Vahan, the Armenians continued the war for 30 years. They won a decisive victory through a peace accord in AD 484, and Armenian Christianity survived. St. Vartan Day-which is celebrated in February of each year-commemorates the battle and is a major Armenian holiday.
The Armenian Church has traditionally maintained two patriarchates: one in Jerusalem and another in Istanbul. In Jerusalem, the Armenian Patriarchate is the guardian of the Holy Places in the possession of the Armenians. It is also one of the three principal custodians of the Church of the Holy Sepulchre and other important shrines and sanctuaries in the Holy Land. The Patriarchate of Constantinople serves a community of approximately 50,000 Armenians living in Istanbul.
Holy Etchmiadzin remains the central spiritual authority for millions of Armenian Christians living in diaspora communities around the globe. In recent years, the Armenian Church has taken an active role in the ecumenical dialogue among the clergy of all faiths.
The Church entered its most recent era of leadership on October 27, 1999, when Armenian Christians elected His Holiness Karekin II as the 132nd Supreme Patriarch and Catholicos of All Armenians, pontiff of the worldwide Armenian Church. He succeeded the deceased Catholicos Karekin I, who died in late June 1999 after leading the church for 4 years.