Zoroaster or Zarathustra (Avestan), also referred to as Zartosht, was an ancient Iranian prophet and the founder of Zoroastrian religion. Zoroastrianism is a religion that was the national religion of the Achaemenid, Parthian and Sasanian dynastic empires of ancient Iran; it is predominantly practiced today by the Iranian Zoroastrian community and Parsi community of India.

Prophet Zoroaster is generally accepted as an authentic historical figure, but the period in which he lived remains unclear. Many scholarly estimates place him circa 1200 BC, making him a candidate to be the founder of the earliest religion based on revealed scripture, while others place him anywhere between the 18th and the 6th centuries BCE.

Zoroaster was a religious reformer of ancient Persia (now Iran) and the founder of the pre-Islamic religion of Zoroastrianism. Thought to have lived about 300 years before Alexander the Great, Zoroaster (Zarathustra in Greek) had a religious vision when he was about 30 years old, and for the next decade traveled throughout Persia preaching and running afoul of the established religious authorities. The story goes that he eventually settled in the land of King Vishtaspa, who embraced Zoroaster's teachings and had his people adopt the new religion.