Emperor Constantine did not make Christianity the official religion of the Roman Empire

That was done by Emperor Theodosius I with the Edict of Thessalonica in 380, 60 years after Constantine’s death.

Kind of tired of seeing this Constantine this/Constantine that stuff pop up all over Reddit/Facebook/Insta/Youtube/etc. It is just absolutely factually incorrect and is one of the weirdest examples of historical scapegoatism I’ve ever seen.

Constantine supposedly had a battlefield conversion on seeing the sign of the cross in the sky. He then supposedly from this experience had a heavy hand in convincing his THREE OTHER CO-EMPERORS IN THE TETRARCHY to initiate the Edict of Toleration, written and put forward by co-emperor Galerius, in which stopped the 2 and a half centuries of legal persecution/murder of Christians as “traitors to the Imperial Cult”. (I say supposedly on these two because there’s some murky history around those events, and his mother may also have been a secret Christian while some say he converted her; he did live most of his life as a pagan). Some people claim this was just realpolitik on his behalf, that he chose Christianity as the perfect uniting religion of the empire, and aside from arguments suggesting it I’ve never seen any direct support of it in contemporary history (it also seems a very odd choice for the unifying religion when just the moment before it was legal to do pretty much anything to a Christian and while it was popular Christians still mostly hid themselves and Christians had a lot of variants going on). I think they mostly point to Constantine having survived all the later civil wars (much later after this edict) of the Tetrarchy to become sole emperor as the main thrust of this thought. But then again, if Constantine became an actual Christian and there’s a law on the books saying that it’s legal to imprison/torture/murder/feed to lions in the arena Christians and people who distributed Christian writings… and you’re one of the four emperors ruling at the time who just converted to Christianity… you can kind of see a personal motivation to get that on the books too. Right? I mean do emperors need even more reasons for assassinations on themselves?

When it was just the two emperors left of the Tetrarchy, Constantine and Licinius, they co-authored the Edict of Milan which gave back the confiscated property of Christians and allowed for full religious freedom in the empire (two things that were not covered in the Edict of Toleration earlier).

You can read the translations of both Edicts here:
https://sourcebooks.fordham.edu/source/edict-milan.asp

What Constantine actually did that I think some people take umbrage with, which started the weird lies about him, is that he arranged for several councils of the bishops of the different sees from Europe/Africa/Asia to come together to define the orthodoxy of the faith. Some people don’t like those early councils, so then they go off on Constantine in a conspiratorial manner. They seem intimately connected in their arguments presented so I am assuming one is driving the other. What we do know about Constantine is that we don’t know what teaching of early Christianity he was following, and that he was baptized on his deathbed by Eusebius of Nicomedia who was an Arian (who were later declared heretical in the later First Council of Nicaea).

Now the real fun question is, why did Emperor Theodosius I make it the official religion of the Empire?

There’s a fun thread on that in the AskHistorians subreddit if you wanna deep-dive:
https://www.reddit.com/r/AskHistorians/comments/1e0ovse/was_christianity_made_the_official_religion_in/