14. Zoroastrianism (2.6 million adherents)
Zoroastrianism is one of the oldest religions in the world. It dates back to the 6th century BC when the prophet, Zoroaster, brought it to the world. However, some believed that it emerged from the prehistoric Indo-Iranian religious system way before that.
The religions spread throughout Iran and its surrounding as the Zoroastrian Achaemenid Empire became the largest ancient empire ever recorded in history in 480 BCE.
It is also believed to have influenced other religions followed, such as Gnosticism, Judaism, Christianity, and Islam. The similarities support that idea.
The basic principal of this religion is truth and honesty. Ahura Mazda is the God of all creation alongside his seven abstract heavenly beings. And a contesting opposite force coexists. It is the Angra Mainyu.
