Sol Invictus

Sol Invictus, also known as Helios, was the official sun god of the later Roman Empire. He was a Syrian sun god whose cult was first promoted in Rome under Elagabalus, but it wasn't until Aurelian came along that Sol Invictus became an official religion. Although there is no consensus on which Syrian solar deity he was, there was general agreement that Sol was of supreme importance, until Constantine abandoned him in favor of Christianity. The last inscription referring to Sol Invictus dates to AD 387, but there were still enough devotees in the fifth century that the Christian theologian Augustine found it necessary to preach against them.