Arguably one of the oldest of the monotheistic faiths, Zoroastrianism is based on the teachings of the Prophet Zarathushtra. Zoroastrianism was the dominant religion of the Persian Empires based on the scriptures, the Avestas, and dealing with devotion to Ahura Mazda, the one god. Zoroastrianism is still practiced today, mainly in parts of Iran and India, but has followers around the world.

Zoroastrianism was the dominant world religion during the Persian empires (559 BC to 651 AC), and was thus the most powerful world religion at the time of Jesus. It had a major influence on other religions. It was the dominant religion there until the seventh century A.D., when Arab forces took control of the land. The Zoroastrian people were presented with two options: become Muslim or die. Although some converted to Islam, many of them, now known as Iranis, stayed in Persia in hiding or disguise. Others, now known as Parsis, fled the country and landed on the shores of India, finding a nation where they could freely practice their religion. The Parsis flourished in India, especially Bombay, for many centuries, and it was fairly recently that the Parsis and Iranis were reunited. Recently, there has been a new trend of Zoroastrians migrating out of India and Iran to other parts of the world, especially Britain, the United States, and Australia.