one of the founders of the Ṣafavid (Ṣafavid Dynasty) state (1501–1736) in Iran.

Ḥaydar inherited the leadership of the Ṣafavid order, a Shīʿite Muslim movement in northwest Iran. He was raised in the city of Amid, but when the Kara Koyunlu empire in western Iran disintegrated in 1467, Ḥaydar moved to Ardabīl (now in northwest Iran), where he formally became the head of the Ṣafavid order. When Ḥaydar married ʿAlamshāh Begum, the daughter of the Ak Koyunlu ruler Uzun Ḥasan, he further strengthened the bonds that existed between the Ak Koyunlu dynasty and the Ṣafavid order.

Ḥaydar continued the policy of his father—a combination of extreme Shīʿite ideology with military activity—by conducting raids against the Christian Circassians of the north in 1483, 1487, and 1488. But his actions soon brought him into conflict with Yaʿqūb, the Ak Koyunlu ruler who was also Ḥaydar's brother-in-law, with the result that the alliance between the order and that dynasty was weakened. Ḥaydar was killed in battle by Ak Koyunlu troops while he was leading an expedition to Circassian territory. Ḥaydar's major achievement was the reliable military organization that he bequeathed to his sons.