What country was the first to have Christianity as an official state religion?

Armenia was the first country in the world to adopt Christianity as its official state religion, in the early 4th century. The church claims to have originated in the missions of two of Jesus' Apostles in the 1st century. Then, in 301 AD, the official state adoption of Christianity in Armenia occurred.

Specifically, Christianity began to spread in Armenia soon after Jesus' death, due to the efforts of his apostles, St. Thaddeus and St. Bartholomew. Before Christianity, Armenians adhered to Armenian paganism (a type of indigenous polytheism).

Accordingly, in May 2001, leaders from America’s Catholic, Protestant and Orthodox Christian communities gathered at Washington’s Catholic Basilica of the National Shrine of the Immaculate Conception to honor a unique milestone in the history of the Christian religion. An ecumenical prayer service was held to mark the 1700th anniversary of Armenia’s conversion to Christianity. The world’s first Christian nation was sincerely honored.