Sassanid (Sassanian) Royal dynasty of Persia (Iran) (ad 224–651). Founded by Ardashir I (r.224–241), the Sassanids revived the native Persian traditions of the Achaemenids, confirming Zoroastrianism as the state religion. There were about 30 Sassanid rulers, the most important after Ardashir being Shapur II (309–379); Khoshru I (531–579), and Khoshru II (590–628), whose conquest of Syria, Palestine, and Egypt marked the height of the dynasty's power. The Sassanids were finally overthrown by the Arabs.

Sassanian of or relating to a dynasty that ruled Persia from the early 3rd century ad until the Arab Muslim conquest of 651; also called Sassanid. The name comes from Sasan, name of the father or grandfather of Ardashir, the first Sassanian.