Upvote:7
Regardless of the validity of the claim that Armenia became Christian in 301 AD, it isn't the first. Osroene - at the time a client state of the Roman Empire - formally adopted Christianity as the state religion under Abgar the Great in 201 AD.
--Samuel Cheetham, A History of the Christian Church During the First Six Centuries, page 58
This source is from 1905; there is another book from 1988 listed as a source on Wikipedia but Google Books doesn't have that page.