Kavad I was the Sasanian King of Kings of Iran from 488 to 531, with a two or three-year interruption. A son of Peroz I (r. 459–484), he was crowned by the nobles to replace his deposed and unpopular uncle Balash.

Inheriting a declining empire where the authority and status of the Sasanian kings had largely ended, Kavad tried to reorganize his empire by introducing many reforms whose implementation was completed by his son and successor Khosrow I. They were made possible by Kavad's use of the Mazdakite preacher Mazdak leading to a social revolution that weakened the authority of the nobility and the clergy. Because of this, and the execution of the powerful king-maker Sukhra, Kavad was imprisoned in the Castle of Oblivion ending his reign. He was replaced by his brother Jamasp. However, with the aid of his sister and an officer named Siyawush, Kavad and some of his followers fled east to the territory of the Hephthalite king who provided him with an army. This enabled Kavad to restore himself to the throne in 498/9.

Bankrupted by this hiatus, Kavad applied for subsidies from the Byzantine emperor Anastasius I. The Byzantines had originally paid the Iranians voluntarily to maintain the defense of the Caucasus against attacks from the north. Anastasius refused the subsidies, which led Kavad to invade his domains, thus starting the Anastasian War. Kavad first seized Theodosiopolis and Martyropolis respectively, and then Amida after holding the city under siege for three months. The two empires made peace in 506, with the Byzantines agreeing to pay subsidies to Kavad for the maintenance of the fortifications on the Caucasus in return for Amida. Around this time, Kavad also fought a lengthy war against his former allies, the Hephthalites; by 513 he had re-taken the region of Khorasan from them.

In 528, war between the Sasanians and Byzantines erupted again, because of the Byzantines refusal to acknowledge Khosrow as Kavad's heir, and a dispute over Lazica. Although Kavad's forces suffered two notable losses at Dara and Satala, the war was largely indecisive, with both sides suffering heavy losses. In 531, while the Iranian army was besieging Martyropolis, Kavad died from an illness. He was succeeded by Khosrow I, who inherited a reinvigorated and mighty empire that equaled that of the Byzantines.

Because of the many challenges and issues Kavad successfully overcame, he is considered one of the most effective and successful kings to rule the Sasanian Empire.