The
Armenian Orthodox Church, also called the
Armenian Apostolic Church, is one of the original
Oriental Orthodox churches, having separated from the then-still-united Catholic/Orthodox church in AD
451 by being excommunicated by the
Council of Chalcedon, which accused the
Armenian church of
monophysitism. The head of the Armenian Orthodox Church is the
Catholicos of Armenia (the plural is
Catholicoi). The
Coptic Orthodox Church was also excommunicated at the same time.
Armenia was the first country to adopt Christianity as its official religion, in AD 301, when Saint Gregory the Illuminator converted the king of Armenia to Christianity.