Khwadāy-Nāmag ("Book of Kings") was a Middle Persian history text from Sasanid era, now lost, imagined first by Theodor Nöldeke to be the common ancestor of all later Arabic-language histories of the Sasanian Empire. It was supposed to have been first translated into Arabic by Abd-Allāh Ibn al-Muqaffaʿ (d. 757 AD), who had access to Sassanid court documents. According to Nöldeke's theory, the book itself was composed first under the reign of Khusraw Anushirvan, and redacted in the reign of the last Sassanid monarch Yazdegerd III (r. 632-651).
This view of Nöldeke's has recently been disproven. 
- The Cambridge History of Iran, v. 3(2), p. 360
- Jackson Bonner, M. R. "Three Neglected Sources of Sasanian History in the Reign of Khusraw Anushirvan" Paris, 2011