Mu'ayyid al-Din Ai-Aba (died July 1174)[1] was the amir of Nishapur from c. 1154 until his death. Although nominally subservient to the Seljuks of Khurasan, he acted as an independent ruler. Due to his control of much of Khurasan, the historian Ibn Funduq called him "Emperor of Khurasan, King of the East."[2]