Hassan al-Mustadi ibn Yusuf al-Mustanjid (1142 – 30 March 1180) is the Abbasid Caliph in Baghdad from 1170 to 1180.

Like his predecessor, he continues to occupy a more or less independent position, with a vizier and courtly surroundings, and supported by only a small force sufficient for an occasional local campaign.

During his reign Saladin ends the Fatimid caliphate, becomes the sultan of Egypt and declared his allegiance to the Abbasids.