In what year did the Sassanid Empire fall?

The Sassanid Empire fell in 651 AD. That year marks the death of Yazdegerd III, the last Sasanian King of Kings, and the effective end of the last pre-Islamic Iranian empire.

The collapse followed decades of strain. The long Byzantine–Sasanian war of 602–628 exhausted the empire’s treasury and military, while court coups and rapid changes of ruler weakened central authority. Arab armies then defeated Sasanian forces at al-Qadisiyyah in 636 and Nahavand in 642.

Yazdegerd III came to the throne in 632 as a child and struggled to coordinate resistance among provincial elites and military commanders. After the defeat at Nahavand, he fled eastward through Iran and Central Asia. A miller killed him near Merv in 651, ending the Sasanian line’s imperial rule.

The conquest was not a single-day event. Arab forces absorbed Sasanian territory over several years, and local resistance continued after 651. Dates such as 637 or 644 refer to important stages in the conquest, not the conventional endpoint of the empire itself.