Sol Invictus, meaning "Unconquered Sun," was a Roman sun god celebrated in ancient Rome. His worship became prominent during the 3rd century CE, particularly under the reign of Emperor Aurelian, who established a festival in his honor on December 25. This date later coincided with the Christian celebration of Christmas. The cult of Sol Invictus represented a blend of various religious traditions, including elements from Mithraism and Hellenistic sun deities. The god was often depicted with a radiant crown and was associated with victory and strength, symbolizing the triumph of light over darkness during the winter solstice.