Sol Invictus

Sol Invictus ("Unconquered Sun") was the official sun god of the later Roman Empire and a patron of soldiers. In 274 AD the Roman emperor Aurelian made it an official cult alongside the traditional Roman cults. Scholars disagree about whether the new deity was a refoundation of the ancient Latin cult of Sol, a revival of the cult of Elagabalus or completely new. The god was favored by emperors after Aurelian and appeared on their coins until Constantine I. The last inscription referring to Sol Invictus dates to AD 387, and there were enough devotees in the 5th century that Augustine found it necessary to preach against them.

The theory dating from the 12th century, that the near-solstice date of 25 December for Christmas was selected because it was the date of the Roman festival of Dies Natalis Solis Invicti (Birthday of the Unconquered Sun) is challenged by some Christian scholars. Different explanations for the date similarity are considered to be "academically thoroughly viable hypotheses" by some. Both theories have supporters, with some claiming that the festival of Dies Natalis Solis Invicti was later syncretized with Christmas and others saying that the Christian celebration may predate the festival of the Dies Natalis Solis Invicti.

Invictus ("Unconquered, Invincible") was an epithet for several deities of classical Roman religion, including the supreme deity Jupiter, the war god Mars, Hercules, Apollo, and Silvanus. It had been in use from the 3rd century BC. The Roman cult to Sol is continuous from the "earliest history" of the city until the institution of Christianity as the exclusive state religion. Scholars have sometimes regarded the traditional Sol and Sol Invictus as two separate deities, but the rejection of this view by S. E. Hijmans has found supporters.

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