Armenians (Armenian: հայեր, hayer [hɑˈjɛɾ]) are an ethnic group native to the Armenian Highlands.Armenians constitute the main population of Armenia and the de facto independent Nagorno-Karabakh Republic.n the early 4th century, the Kingdom of Armenia became the first state to adopt Christianity as a state religion, by which previously predominant Zoroastrianism and paganism in Armenia gradually declined.