Rukn-ud-Dīn Khurshāh (or Khwarshāh) (?-1256) was the son of ‘Alā’ ad-Dīn Muḥammad III and the 27th Imām of the Nizārī Ismā'īlī Shia community. He was also the 5th and final Imam who ruled at Alamut. The Imam was the eldest son of Imam ‘Ala al-Din Muhammad and succeeded his murdered father to the Imamate in 1255. Imam Rukn al-Din engaged in a long series of negotiations with the invading Mongols, and under whose leadership, the Alamut Castle was surrendered to the Mongol Empire.