Bundahishn (Middle Persian: , "Primal Creation") is the name traditionally given to an encyclopedic collection 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 Islam in Iran, and in yet other cases, such as the idea that the Moon is farther than the stars, it reiterates scripture even though science had, by then, determined otherwise.
The Bundahishn survives in two recensions: an Indian and an Iranian version. The shorter version was found in India and contains only 30 chapters, 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). It contains 36 chapters. The Bundahisn contains characteristics that fall under the rubric of different forms of classifications, including both as an encyclopedic text and as a text similar to midrash.
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.