One of the oldest revealed religions (if not the oldest), Zoroastrianism developed in ancient Persia and played a role in the evolution of the Judaic, Christian, and Islamic belief systems. Heavily dualistic in its beliefs, the community that was for so long based in the lands of modern-day Iran has been greatly diminished and dislocated; at the beginning of the 21st century, the largest group of believers, known as Parsis (Parsees), reside in India. This entry will outline the basic tenets of the Zoroastrian faith, give a short history of the tradition, and attempt to show some ways in which scholars have envisioned Zoroastrian influence on many major world religions.