The Buyyids or Buwayhids or Al-e Buyeh, were a Shi'ite tribal confederation from Daylam, a region on the southern shore of the Caspian Sea.
In pre-Islamic times they had served as mercenaries for the Sasanian kings of Iran, but were independent from their rule. They were considered a formidable military force, especially because of their ability as foot soldiers. Succession of power was hereditary, with fathers dividing their land among their sons. During the time of Haroon al-Rashid, the Alid people sought refuge among them.
The start of the Buwayhid confederation was led by Ali b. Buya and his two younger brothers, al-Hasan and Ahmad. After having secured a partnership with an important Persian landowner named Zayd b. Ali al-Nawbandajani, Ali was able to recruit an army to defeat a Turkish general from Baghdad named Yaqut (General) in 934 CE. After that they established power within the crumbling Abbasid Empire in the form of a confederation rather than a new empire. They were known for the revival of Persian culture. Buwayhid leaders were known as Shâhanshâh, literally king of kings.
During the 900s, Buwayhid dynasties took power in Fars (southwestern Iran, 934-1062); Rayy (977-1029); Jibal (932-1028); Kerman (936-1048). From 945-1055, a Buwayhid dynasty ruled Baghdad and most of Iraq.
During the mid 11th century CE the Buwayhid dynasties all fell to the Seljuks or their allies.