Zarathustra (in Greek, Zoroaster) was a Persian prophet who at the age of 30 believed he had seen visions of God, whom is Ahura Mazda, the creator of all that is good and who alone is worthy of worship. This was a departure from previous Indo-Persian polytheism, and Zarathustra has been termed the first non-biblical monotheist.
There is disagreement among scholars as to exactly when and where Zarathustra lived, but most agree that he lived in eastern Iran around the sixth century BCE.
Zoroastrianism became the official religion of the Persian Empire, but it virtually disappeared in Persia after the Muslim invasion of 637 CE. Only about 10,000 survive in remote villages in Iran, but over the centuries many sought religious freedom in India. Today, most Zoroastrians are in India, where they are called Parsiis and number about 200,000.