Zurvanism is a now-extinct branch of Zoroastrianism that had the divinity Zurvan as its First Principle (primordial creator deity). Zurvanism is also known as Zurvanite Zoroastrianism.

In Zurvanism, Zurvan is the god of infinite time (and space) and is aka (“one", "alone”) deity of matter. Zurvan is the parent of the two opposites representing the good god Ahura Mazda and the evil Angra Mainyu. Zurvan is regarded as a neutral god; being without gender (neuter), passion, one whom there is no distinction between good or evil. Zurvan is also the god of destiny, light and darkness. 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-, "time" or "old age".

Zurvanites considered Ahura Mazda and Spenta Mainyu one of two equal-but-separate divinities under the primacy of Zurvan. The central Zurvanite belief made Ahura Mazda the middle god and Angra Mainyu the fallen twin brother.

Mazdeans consider the divinity of Ahura Mazda the transcendental creator. Their central belief makes Ahura Mazda the supreme god and Spenta Mainyu and Angra Mainyu twin brothers.