Abu ‘Ali Mansur Tāriqu l-Ḥākim, called Al-Hakim bi Amr al-Lāh (Arabic: literally "Ruler by God's Command"), is the sixth Fatimid caliph and 16th Ismaili imam (996–1021).

Al-Hakim is an important figure in a number of Shia Ismaili religions, such as the world's 15 million Nizaris and in particular the 2 million Druze of the Levant whose eponymous founder Ad-Darazi proclaims him as the incarnation of God in 1018.

In Western literature he has been referred to as the "Mad Caliph", primarily as a result of the Fatimid desecration of Jerusalem in 1009, though this title is disputed as stemming from partisan writings by some historians (such as Willi Frischauer and Heinz Halm).

Histories of Al Hakim can prove controversial, as diverse views of his life and legacy exist.