Armenia was the first state traditionally recognized as adopting Christianity as its official religion. The conversion is usually dated to AD 301, during the reign of King Tiridates III.
According to Armenian tradition, Tiridates converted after being healed and instructed by Gregory the Illuminator, a Christian imprisoned by the king before becoming Armenia’s first Catholicos. Christianity had already reached Armenia, possibly through the apostles Thaddeus and Bartholomew, but the royal proclamation made it a state faith.
The decision also had geopolitical importance. Armenia sat between the Roman and Iranian worlds, and Christianity helped distinguish the kingdom from its Zoroastrian-influenced neighbors, especially the Sasanian Empire. The Armenian Apostolic Church later became a major guardian of Armenian culture and identity.
The exact date is debated: some historians favor dates around 301, while others place the formal conversion later, between roughly 314 and 325. That dating debate does not usually change the standard quiz answer. Georgia and the Roman Empire adopted Christianity as a state religion later.