Al-Āmir bi-Aḥkām Allāh, Abū ʿAlī Manṣūr b. Abī al-Qāsim Aḥmad al-Mustaʿlī bi’llāh (r. 495–524/1101–1130) was the tenth Fāṭimid caliph. He was born in Cairo on Tuesday 13 Muḥarram 490/31 December 1097 and was only five years old when his father died (495/1101). Al-Mustaʿlī’s vizier al-Afḍal b. Badr al-Jamālī (q.v.) placed him on the throne with the title of al-Āmir bi-Aḥkām Allāh and he himself took charge of running the affairs of the state.

At that time the Crusaders, who had already captured Jerusalem in 492/1099, went on to seize many of the towns and fortresses o…