Christianity first spread to Armenia prior to the official adoption of the faith in the early fourth century, although the details are obscure. In the early fourth century, the Kingdom of Greater Armenia adopted Christianity as its state religion, becoming the first state to do so. The Arsacid king of Armenia at the time, Trdat, was converted by Gregory the Illuminator, who became the first head of the Armenian Church. The traditional date for the conversion of Armenia is 301, although many alternative dates have been proposed by scholars. While Armenia's church structure was established at this time, it took longer for Christianity to fully take root in the country. The greatest progress came after the invention of the Armenian alphabet by Mesrop Mashtots and the translation of the Bible and liturgy into Armenian in the fifth century.

Armenia, also the Kingdom of Greater Armenia, or simply Greater Armenia or Armenia Major sometimes referred to as the Armenian Empire, was a kingdom in the Ancient Near East which existed from 331 BC to 428 AD. Its history is divided into the successive reigns of three royal dynasties: Orontid, Artaxiad and Arsacid (52–428).