Mithra(s) was a Roman god, and the subject of the December 25th festival. History says that Mithra was the first immaculate conception and born on December 25th - the son of the Sun God, so also known as son of God. The creation of the world is central to the Mithraic mythology.
This was a significant god and a significant Roman religion with its mysteries. There were many temples and sanctuaries to Mithra, and Mithraism is viewed as a rival of early Christianity.
It is generally held that the Christians appropriated the festival of Mithras' birth celebration on December 25th - the winter solstice - with similar light metaphors and correspondence between Christ and the sun.
Considering they were rival religions, the Mithraists faced persecution from the Christians in the 4th century when Constantine ruled. This religious community disappeared.
What fascinates me is how successful the Christians were at banishing all other religions. They termed all of them as 'pagan'.
As a definition, pagan was rustic, unlearned, bumpkin, villager, country dweller, and so on. It became an all-embracing, pejorative term for polytheists. It was us vs them.
This approach worked, but It brings baggage. That means that when today's biblical historians are tracing the roots of various holidays and festivals they always find themselves in "pagan" territory. Remember John Milton who as a Puritan was part of the banishment of Christmas based on its origins as a "pagan" festival.
So any time you read about the Christmas traditions in those" four things you might not know about Christmas" articles on the internet, you will inevitably find Mithras in the mix of the discussion. | 
