Zoroastrianism is an early monotheist religion that was founded by Zarathushtra (Zoroaster to Greece, Zarthosht to India and Persia). Zorostrianism religion is based on the Avesta, ancient scriptures written in old Iranian which have been corrupted and damaged over time. The religion is estimated to have begun sometime around 1500 BCE.
Zoroastrianism appears to have begun as a spiritual expression of a peaceful group of people in Persia, modern day Iran, who called themselves people of righteousness (asha). These people had enemies, a polytheist majority which they referred to as the People of the Lie (druj). In its origins, Zoroastrianism began with a single divine spirit, Ahura Mazdah. Gradually, six dieties were named as aspects of Ahura Mazdah (called the Amesha Spentas). As time went on, these abstract representations of the single god were personnified in many texts, somewhat like archangels. The Zoroastrian gods had opposing evil spirits with whom they were constantly at war. The leader of these spirits was known as Ahriman.
Zoroastrianism had some influence on Judaism, and consequently, Christianity over the years. In 650 CE, Islamic Arabs invaded Persia and many of the Zoroastrian followers fled to India. An estimated 140,000 people still practice Zoroastrianism today, mostly within India, but several remain in Iran, and some have spread across to North America.