The Battle of al-Qadisiyyah was fought between the Rashidun Caliphate and the Sasanian Empire. It occurred during the early Muslim conquests and marked a decisive victory for the Rashidun army during the Muslim conquest of Persia.

The Rashidun offensive at Qadisiyyah is believed to have taken place in November of 636; at the time, the Sasanian army was led by Rostam Farrokhzad, who died in uncertain circumstances during the battle. The collapse of the Sasanian army in the region led to a decisive Arab victory over the Iranians, and the incorporation of territory that comprises modern-day Iraq into the Rashidun Caliphate.

Arab successes at Qadisiyyah were key to the later conquest of the Sasanian province of Asoristan, and were followed by major engagements at Jalula and Nahavand. The battle allegedly saw the establishment of an alliance between the Sasanian Empire and the Byzantine Empire, with claims that the Byzantine emperor Heraclius married off his granddaughter Manyanh to the Sasanian king Yazdegerd III as a symbol of the alliance.