Al-Hakim I (Arabic: أبو العباس أحمد الحاكم بأمر الله; full name: , Abū l-ʿAbbās Aḥmad al-Ḥākim bi-amr Allāh ibn Abi 'Ali al-Hasan ibn Abu Bakr; c. 1247 – 19 January 1302) was the second Abbasid caliph whose seat was in Cairo and who was subservient to the Mamluk Sultanate.
When Baghdad fell to the Mongols in 1258, al-Hakim I escaped to Damascus where he befriended the Arab tribal chief 'Isa ibn al-Muhanna, who tried to set him up as caliph, but in the confusion surrounding the Mongol invasion of Syria in 1259–1260, he ended up in Aleppo, where he was proclaimed.
Only about fifty troops escaped with al-Hakim, who, making his way back to Cairo and after a careful scrutiny of his genealogical claim to be an Abbasid, was proclaimed caliph in succession to al-Mustansir in 1262.
Since al-Hakim's connection with the Abbasids is distant and faint, it cannot now be determined whether he was really from that family as he claimed or not.
Although he was kept in office after 1262, the Mamluk sultans kept him as a virtual prisoner in the citadel, until Sultan Lajin released him in December 1296, allowing him to live in a house in the city and giving him a bigger financial emolument.