Proto-Indo-Iranian religion: The various beliefs and practices from which the later indigenous religion of the Iranian peoples evolved.
Zoroastrianism: The present-day umbrella term for the indigenous native beliefs and practices of the Iranian peoples. While present-day Zoroastrianism is monolithitic, a continuation of the elite form of Sassanid times, in antiquity it had several variants or denominations, differing slightly by location, ethnic affiliation and historical period. It once has large population and high diversity.
Mandaeism: A gnostic monotheism of (at the latest) the 1st century CE observed Mandā d-Heyyi - "Knowledge of Life". Mandaean theology is based more on a common heritage than on any set of religious creeds and doctrines.
Manichaeism: 3rd century ditheistic gnosticism that may have been influenced by Mandaeism. Manichaens believed in a "Father of Greatness" (Aramaic: Abbā dəRabbūṯā, Persian: pīd ī wuzurgīh) and observed Him to be the highest deity (of light).
The early Islamic period saw the development of Persian mysticism, a traditional interpretation of existence, life and love with Perso-Islamic Sufi monotheism as its practical aspect. This development believed in a direct perception of spiritual truth (God), through mystic practices based on divine love.
Khurramites, a 9th-century religious and political movement based on the 8th century teachings of Sunpadh, who preached a syncretism of Shia Islam and Zoroastrianism. Under Babak Khorramdin, the movement sought the redistribution of private wealth and the abolition of Islam.
Behafaridians, an 8th-century cult movement around the prophet Behafarid. Although the movement is considered to have its roots in Zoroastrianism, Behafarid and his followers were executed on charges (made by Zoroastrians) of harm to both Zoroastrianism and Islam.
Yarsan, a religious order of Yazdanism, which is believed to have been founded in the 16th century. Yazdanism promulgated the belief in a God manifest as one primary and five secondary avatars to form with God the Holy Seven.