Deities of Medo-Persia. The indications are that the kings of the Medo-Persian Empire were Zoroastrians. While it cannot be proved or disproved that Cyrus the Great adhered to the teachings of Zoroaster, from the time of Darius I the inscriptions of the monarchs repeatedly refer to Ahura Mazda, the principal deity of Zoroastrianism. Darius I referred to Ahura Mazda as the creator of heaven, earth, and man, and he looked to this god as the one who had bestowed upon him wisdom, physical skillfulness, and the kingdom.

A characteristic feature of Zoroastrianism is dualism, that is, the belief in two independent divine beings, one good and the other evil. Ahura Mazda was viewed as the creator of all good things, whereas Angra Mainyu was regarded as the creator of all that is evil. It was thought that the latter could bring about earthquakes, storms, disease, and death as well as stir up unrest and war. Lesser spirits were believed to assist these two gods in carrying out their functions.

The symbol of the god Ahura Mazda was much like the representation of the Assyrian Asshur, namely, a winged circle, from which, at times, a bearded man with the vertical tail of a bird emerges.

Ahura Mazda may have figured in a triad. This is suggested by the fact that Artaxerxes Mnemon invoked the protection of Ahura Mazda, Anahita (a goddess of water and of fertility), and Mithra (a god of light), and he attributed his reconstruction of the Hall of Columns at Susa to the grace of these three deities.

The Zend-Avesta, the sacred Zoroastrian writings, actually contain prayers to fire, to water, and to planets as well as to the light of the sun, moon, and stars. Fire is even referred to as the son of Ahura Mazda.