what country was the first to have christianity as an official state religion
State religion Official religions have been known throughout human history in almost all types of cultures, reaching into the Ancient Near East and prehistory. The relation of religious cult and the state was discussed by Varro, under the term of theologia civilis ("civic theology"). The first state-sponsored Christian church was the Armenian Apostolic Church, established in 301 AD.[1] In Christianity, as the term church is typically applied to a Christian place of worship or organisations incorporating such ones, the term state church is associated with Christianity as sanctioned by the government, historically the state church of the Roman Empire in the last centuries of the Empire's existence, and is sometimes used to denote a specific modern national branch of Christianity. Closely related to state churches are ecclesiae, which are similar but carry a more minor connotation.
Byzantine Empire Several signal events from the 4th to 6th centuries mark the period of transition during which the Roman Empire's Greek East and Latin West divided. Constantine I (r. 324–337) reorganised the empire, made Constantinople the new capital, and legalised Christianity. Under Theodosius I (r. 379–395), Christianity became the Empire's official state religion and other religious practices were proscribed. Finally, under the reign of Heraclius (r. 610–641), the Empire's military and administration were restructured and adopted Greek for official use instead of Latin.[4] Thus, although the Roman state continued and Roman state traditions were maintained, modern historians distinguish Byzantium from ancient Rome insofar as it was centred on Constantinople, oriented towards Greek rather than Latin culture, and characterised by Orthodox Christianity.[3]