The Bavand dynasty (باوندیان) (also spelled Bavend), or simply the Bavandids, was an Iranian dynasty that ruled in parts of Tabaristan (present-day Mazandaran province) in what is now northern Iran from 651 until 1349, alternating between outright independence and submission as vassals to more powerful regional rulers. They ruled for 698 years, which is the second longest dynasty of Iran after the Baduspanids.
The dynasty itself traced its descent back to Bav, who was alleged to be a grandson of the Sasanian prince Kawus, brother of Khosrow I, and son of the shah Kavad I (ruled 488–531), who supposedly fled to Tabaristan from the Muslim conquest of Persia. He rallied the locals around him, repelled the first Arab attacks, and reigned for fifteen years until he was murdered by a certain Valash, who ruled the country for eight years. Bav's son, Sohrab or Sorkab (Surkhab I), established himself at Perim on the eastern mountain ranges of Tabaristan, which thereafter became the family's domain. The scholar J. Marquart, however, proposed an alternative identification of the legendary Bav with a late-6th-century Zoroastrian priest ("magian") from Ray. Parvaneh Pourshariati, in her re-examination of late Sasanian history, asserts that this Bav is a conflation of several members of the powerful House of Ispahbudhan: Bawi, his grandson Vistahm and his great-nephew Farrukhzad. She also reconstructs the events of the middle 7th century as a civil war between two rival clans, the Ispahbudhan and Valash's House of Karen, before the Dabuyid Farrukhan the Great conquered Tabaristan and subdued the various local leaders to vassalage. The Dabuyid house then ruled Tabaristan until the Abbasids subdued the region in 760.
It is at the time after the Abbasid conquest that the Bavandids enter documented history, with Sharwin I, in later tradition accounted the great-grandson of Surkhab I. The dynasty is commonly divided into three major branches: the Kayusiyya, named after Kayus ibn Kubad, the Arabicized name of the family's legendary ancestor Kawus son of Kavad, which ruled from 665 until 1006, when the family's rule was ended by Qabus ibn Wushmagir.