In terms of geography, the Armenian homeland is not too far from the Holy Land, where Jesus preached and was crucified. There is even a tradition of correspondence between one King Abgar of Edessa and Jesus, in which the king invited Jesus to visit him and perform his wonders in Edessa. Jesus promised to send someone from his followers.
And in fact, after the events recorded in the Bible, two of Jesus’ apostles, Thaddeus and Bartholomew, would supposedly spread the knowledge of the Gospel to the north, namely, Anatolia, Asia Minor, and the Caucasus.
It took a few centuries for Christianity to form as a religion though. In the meantime, it has been famously persecuted in the Roman Empire, as well as in Greater Armenia. Armenian King Tiridates III, who had been educated in Rome and wore his own crown in spite of being closely tied to the Roman Empire, ensured that the followers of Jesus were not free to maintain the religion in his domain, subjecting them to punishments. Among the king’s oppressions can be noted the martyrdom of the nuns Hripsime and Gayane, as well as the group they lead away from Rome and away from the persecutions of Emperor Diocletian.
One follower of Jesus was a man named Gregory, who was a member of a noble family that had for its part been subjected to Tiridates’s persecutions due to political reasons. Gregory received his education in Caesarea (Kayseri in Turkey today) and was later ordained a bishop. He would eventually offer his services to Tiridates back in Armenia, but his lineage and religion would be uncovered. Gregory refused to worship the idol that was venerated by the king and his court, which resulted in his 13-year imprisonment in Khor Virap (“a deep dungeon”, now the site of a church of the same name). Traditionally, it is believed that angelic visitations and covert assistance by Christians and pagans had kept him alive over the course of those years.
Shortly, King Tiridates fell ill and couldn’t be cured by anyone in the land. King’s sister Khosrovidoukth had a vision urging her to have Gregory released and have him cure the king through prayer. Having been cured, Tiridates converted to Christianity and had his entire kingdom do the same. Gregory would serve as the first Catholicos (the head of the Armenian Church), marking a major turning point in the Armenian history. Now, Gregory is known as St. Gregory the Illuminator (Sourp Grigor Lousavorich in Eastern Armenian pronunciation, Sourp Krikor Lousavorich in Western Armenian).
Quite definitely, most of this story’s elements bear a traditional value rather than strictly historical. The date of Armenia’s conversion to Christianity, 301 AD, is likewise a subject of debate. The Roman Empire is considered to have publicly allowed Christianity ten years later. In terms of all events, tradition accepts that Armenians were the very first people to adopt Christianity as a state and national religion, which remains a key aspect of the Armenian identity until today.