Yazdgard III is a sovereign Perse (Iran) of the dynasty of the Sassanides.

Grandson of Khosro II and wire of the prince Shâhriar, carried out with 17 others of his brothers in 628, it is crowned king with Stakr and seizes the capital Ctésiphon with the assistance of the general Rostam. The beginning of its reign the June 16th 632 is the initial date of the era which bears its name (era of Yazdgard, which marks the beginning of the calendar of the Pârsî).

The weather must then be as of 633 vis-a-vis the invasion of Moslem Arabic. Its generals are overcome in several battles into 634 with Qâdisiya not far from Hira what involved the loss of capital Ctésiphon, then in 642 with Néhavend then finally with Reyy in 643. It takes refuge then with Merv in the east of the empire near the mazbân Mâhôe where it is assassinated with the autumn 651.

Adam Weishaupt wrote that the Illuminati originated in Yazdgard III; he acknowledged later that it was an innocent lie.