The main concepts used in this article are the dichotomy and differences between the two main groups of theories regarding the origins of the Roman mystery cult of Mithras: namely the school of the great Belgian scholar Franz Cumont, who considered Mithraism in the Roman world as an essentially Iranian cult adapted to the new cultural Hellenistic-Roman context and the theory of the 19th century German scholar K. B. Stark, respectively (revived in the seventies of the 20th century by academics like R. Beck, J. R. Hinnells, St. Insler, R. Gordon, and A. Bausani), who considered that the Roman cult of the solar god Mithras was a new mystery cult, which was born in the Roman world because of the Hellenistic scientific discovery of the precession of the equinoxes. My conclusion is that the Roman cult of Mithras, fused with the cult of Sol Invictus (the Hellenistic-Roman cult of the Unvanquished Sun), has more things Iranian than the name of the central deity of this initiation-mystery cult (despite its undeniable Hellenistic-Roman and astrological-astronomical elements).