Zoroaster (ca. 628 BC- ca. 551 BC) was a prophet of ancient Iran and the founder of the Iranian national religion. Zoroastrianism is ranked with Judaism, Christianity, and Islam among the higher religions originating in the Middle East.

The dates given for Zoroaster by ancient and modern writers differ considerably. The more sober authors have placed him between 1000 and 600 B.C. The latter date conforms to the tradition of the Zoroastrians themselves, who regard Zoroaster as having revealed his religion 258 years before Alexander the Great conquered Iran in 331 B.C. The main sources for the life and career of Zoroaster are the Avesta, the sacred book of the Zoroastrians, the oldest and most reliable source; later Zoroastrian literature, among which Denkart, an encyclopedic work in Middle Persian, stands out; and non-Zoroastrian works, which include Persian, Arabic, Armenian, and classical histories.

Zoroaster was known among the classic writers chiefly as the...