Zoroastrianism (also known as Zarathustrianism, Mazdaism, and Parseeism or Parsees in India) is a monotheistic religion of ancient Persia based on the teachings of Zoroaster (628-551 BC) (in Greek pronounciation) (Zarathustra), the prophet of Zoroastrianism and its deity Ahura Mazda. To become Zoroastrian you have to essentially be born into it, and thus it is considered a dying and minor religion surviving with 150,000-200,000 Zoroastrians in the world. They are mostly found in India, Iran, Iraq, and Pakistan.
There is sparse detail on the biography of Zoroaster with a lot of legendary type things associated with him. Zoroaster was very high in character and initially trained to be a priest. At age 20 he left his wife and child to seek higher enlightenment. At the age of 30 he ultimately became the prophet of Ahura Mazda near the Dante River through received visions. Ahura Mazda resembles the ancient Jewish God exceptionally.