Zurvanism is a fatalistic religious movement of Zoroastrianism in which the divinity Zurvan is a first principle (primordial creator deity) who engendered equal-but-opposite twins, Ahura Mazda and Angra Mainyu. Zurvanism is also known as "Zurvanite Zoroastrianism", and may be contrasted with Mazdaism.
In Zurvanism, Zurvan was perceived as the god of infinite time and space and was aka ("one", "alone"). Zurvan was portrayed as a transcendental and neutral god, without passion, and one for whom there was no distinction between good and evil. The name Zurvan is a normalized rendition of the word, which in Middle Persian appears as either Zurvān, Zruvān or Zarvān. The Middle Persian name derives from Avestan zruvan- (𐬰𐬭𐬬𐬀𐬢, time), which is grammatically neuter.
Although the details of the origin and development of Zurvanism remain murky (for a summary of the three opposing opinions see below), it is generally accepted that Zurvanism was: 1) a branch of greater Zoroastrianism; 2) a sacerdotal response to resolve a perceived inconsistency in the sacred texts (see below); and 3) probably introduced during the second half of the Achaemenid era.
Zurvanism enjoyed royal sanction during the Sasanian Empire (226–651 CE) but no traces of it remain beyond the 10th century. Although Sasanian-era Zurvanism was certainly influenced by Hellenic philosophy, any relationship between it and the Greek divinity of Chronos "Time" has not been conclusively established. Non-Zoroastrian accounts of typically Zurvanite beliefs were the first traces of Zoroastrianism to reach the west, leading European scholars to conclude that Zoroastrianism was a monist religion, an issue of controversy among both scholars and contemporary practitioners of the faith.
Zurvan appears in Sanskrit as sarva, and the etymology of Sarvastivada, a monistic Buddhist sect, suggests at least a common conceptional link to Zurvanism, depending on how the word Sarvastivada is parsed.
Mythology was important to Zurvanism.