The Zoroastrian religious tradition of ancient Iran represents one of the oldest surviving religious systems and one whose influence on Western religious thought — through Judaism, Christianity, and Islam — is debated but probably real.

Zarathustra (Zoroaster), the prophet of the religion, is dated by scholars anywhere from 1500 BC to 600 BC based on linguistic analysis of the Gathas (the oldest Zoroastrian hymns) and the absence of secure external references. The religion he founded centers on the cosmic dualism of Ahura Mazda (the Wise Lord, creator of truth and light) and Angra Mainyu (the Destructive Spirit), and the human role in the ongoing cosmic struggle between them through thought, word, and deed.

The Zoroastrian eschatology — the idea of a final renovation of the world (Frashokereti), a final judgment of souls, a resurrection of the body, and the ultimate defeat of evil — is notably similar to the eschatological developments in post-exilic Judaism that then flow into Christianity and Islam. The contact between Jewish and Zoroastrian thought during the Babylonian exile and the Persian period is the most plausible vector of transmission, but direct textual evidence is limited.

The survival of Zoroastrianism in the face of the Islamic conquest of Iran in the 7th century AD — through the small communities of Zoroastrians who resisted conversion and eventually emigrated to India (the Parsis) — is one of the remarkable stories of religious continuity in world history. The Parsi community in India has preserved Zoroastrian texts, rituals, and religious tradition for 1,300 years in a diaspora context.