Supreme god of ancient Iranian religion, especially Zoroastrianism. Ahura Mazda was worshiped by Darius I and his successors as the greatest god and the protector of the just king. Zoroaster taught that Ahura Mazda created the universe and maintains the cosmic order, and that the history of the world consists of the battle between two spirits he created—the beneficent Spenta Mainyu and the destructive Angra Mainyu. The Avesta identifies Ahura Mazda himself with the beneficent spirit and represents him as bountiful, all-knowing, and the creator of everything good. In late sources (from the 3rd century), Zurvan (“Time”) is the father of the twins Ormazd (Ahura Mazda) and Ahriman (Angra Mainyu), who in orthodox Mazdaism (Zoroastrianism and Parsiism) reign alternately over the world until Ormazd's ultimate victory.
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It is commonly supposed (Thieme 1960:308; Gershevitch 1964:23; Kuiper 1983:682) that Indo-Iranian *Asura was the proper name of a specific divinity, with whom other divinities were then identified. In this sense, ahura is not a noun but an adjective meaning "ahuric".
For not altogether obvious reasons, the Oxford English Dictionary lists asura, rather than ahura, as a Zoroastrian term.
In the Gathas, the poet does not specify which of the divinities aside from Ahura Mazda he considers to be ahuras. While Ahura Mazda is unambiguously "the mightiest Ahura" (Yasna 33.11), in the only two occurrences of the term where the word does not refer to Ahura Mazda, the poet uses the expression mazdasca ahurano (Yasna 30.9, 31.4). This phrase, generally understood to mean "the Wise [Mazda] One and the (other) Ahuras", it is in "common opinion" (Boyce 1975:159) recognized as being archaic with the "other Ahuras" being Indo-Iranian *mitra, *varouna and the predecessors of the other RigVedic Adityas.
In the Younger Avesta, three divinities of the Zoroastrian pantheon are repeatedly identified as ahuric. These three are Ahura Mazda, Mithra and Apam Napat, and hence known as the "Ahuric triad". Other divinities with whom the term "Ahuric" is associated include the six Amesha Spentas and (notable among the lesser yazatas) Aredvi Sura of The Waters and Ashi of Reward and Recompense.