The Pishdadian dynasty (دودمان پیشدادیان) is a mythical line of primordial kings featured in Zoroastrian belief and Persian mythology, who are presented in legend as originally rulers of the world but whose realm was eventually limited to Ērānshahr or Greater Iran. Although there are scattered references to them in the Zoroastrian scriptures the Avesta and later Pahlavi literature, it is through the 11th century Iranian national epic, the Shahnameh, that the canonical form of their legends is known. From the 9th century, Muslim writers, notably Tabari, re-told many of the Pishdadian legends in prose histories and other works. The Pishdadian kings and the stories relating to them have no basis in historical fact, however.
According to the Shahnameh, the Pishdadians were the first Iranian dynasty, pre-dating the historical Achaemenids, and ruling for a period of over two thousand years. Their progenitor was Keyumars, the first human and the “Zoroastrian Adam”. He was followed by his descendants who, as kings of the world, fought demons and improved the lives of humankind by introducing them to new knowledge and skills. His most renowned successor, Jamshid, established the main elements of civilization, but, as a result of his pride and hubris, was overthrown by the evil tyrant Zahhak. Following a popular insurrection against Zahhak, the throne was eventually restored to the Pishdadians. However, the next king, Fereydun, divided the world between his three sons with his youngest, Iraj, receiving Iran, the choicest portion, after whom it is named. Iraj and his successors aroused the envy of the other descendants of Fereydun leading to a lengthy feud and series of wars which eventually caused the downfall of the dynasty. The Shahnameh tells how the Iranians, having no confidence in the last of the Pishdadians, replaced them with another mythical dynasty, the Kayanians.
Tabari repeated many of the same stories in his History, with some variations.