The State That Adopted Christianity Before Rome Did

The Armenian church traces its catholicosate to Gregory the Illuminator, traditionally credited with converting King Tiridates III and establishing Christianity as the state religion of Armenia at the start of the fourth century, an adoption tradition places before the Roman Empire's own toleration and later establishment of Christianity under Constantine and his successors, making Armenia, on the traditional dating, an early and possibly the first state to adopt Christianity officially, though the precise year is debated among historians working from limited and not fully consistent early sources.

The Armenian church subsequently rejected the christological definition of the Council of Chalcedon in 451, placing it, along with the Georgian church for several further centuries and the Assyrian Church of the East on separate grounds again, outside full communion with both Rome and Constantinople from an early date, so the catholicosate of these churches developed in genuine doctrinal as well as geographic independence from the imperial church, a separation that has persisted for over fifteen centuries and that modern ecumenical dialogue between these churches and the Chalcedonian traditions has only partially addressed.