Atabeg is a title of nobility of Turkic origin, indicating a governor of a nation or province who was subordinate to a king or Emperor but senior to a Khan.
The title of Atabeg was common during the Seljuq rule of the near-east starting in the 12th century. It was common in Mesopotamia (now Iraq) and Persia (now Iran). The most famous Atabeg was perhaps Zengi, who became Atabeg of Mosul in 1128 and soon established himself as an independent ruler of much of northern Mesopotamia and Syria (including Aleppo). After the end of Seljuq rule the title was used only intermittently.
