Bundahishn, meaning "Primal Creation", is the name traditionally given to an encyclopædiaic collections of Zoroastrian cosmogony and cosmology written in Book Pahlavi. The original name of the work is not known.
Although the Bundahishn draws on the Avesta and develops ideas alluded to in those texts, it is not itself scripture. The content reflects Zoroastrian scripture, which in turn reflects both ancient Zoroastrian and pre-Zoroastrian beliefs. In some cases, the text alludes to contingencies of post-7th century Islamic Iran, and yet in other cases (e.g. in the idea that the moon is further away than the stars) reiterates scripture even though science had by then determined otherwise.
The traditionally given name seems to be an adoption of the sixth word from the first sentence of the younger of the two recensions. The older of the two recensions has a different first line, and the first translation of that version adopted the name Zand-Ākāsīh, meaning "Zand-knowing", from the first two words of its first sentence.
Most of the chapters of the compendium date to the 8th and 9th centuries, roughly contemporary with the oldest portions of the Denkard, which is another significant text of the "Pahlavi" (i.e. Zoroastrian Middle Persian) collection. The later chapters are several centuries younger than the oldest ones. The oldest existing copy dates to the mid-16th century.
The Bundahishn survives in two recensions. A shorter was found in India, and is thus known as the Lesser Bundahishn, or Indian Bundahishn. A copy of this version was brought to Europe by Abraham Anquetil-Duperron in 1762. A longer version was brought to India from Iran by T.D. Anklesaria around 1870, and is thus known as the Greater Bundahishn or Iranian Bundahishn or just Bundahishn. The greater recension (the name of which is abbreviated GBd or just Bd) is about twice as long as the lesser (abbreviated IBd).