Abu Muhammad Hasan ibn Yusuf al-Mustanjid (; 1142 – 27 March 1180) usually known by his regnal title al-Mustadi () was the Abbasid Caliph in Baghdad from 1170 to 1180. He succeeded his father al-Mustanjid in 1170 as the Caliph. Biography Al-Mustadi was the son of caliph al-Mustanjid and his mother was Ghadha. He was born in 1142. His full name was Hasan ibn Yusuf al-Mustanjid and his Kunya was Abu Muhammad. He was named after 5th caliph al-Hasan. When his father al-Mustanjid died on 18 December 1170, he succeeded him. Al-Mustadi's reign is noted in general for its extensive building activities. He is said to have rebuilt al-Taj palace in Baghdad which was first constructed by 10th-century Abbasid caliph al-Muktafī (r. 902–908) and there was a great construction project of mosques, schools, religious endowments in his reign. His two spouses Sayyida Banafsha and Zumurrud Khatun, where especially prolific in these efforts. Banafsha was the follower of Hanbali school of thought, ordered the construction of a bridge in Baghdad in 570 AH/1174 CE, that was named after her. Like his predecessor, he continued 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 ended the Shia Fatimid Caliphate, became the Sultan of Egypt and declared his allegiance to the Abbasids. Towards the end of 1169, Saladin, with reinforcements from Nur ad-Din, defeated a massive Crusader-Byzantine force near Damietta. Afterward, in the spring of 1170, Nur ad-Din sent Saladin's father to Egypt in compliance with Saladin's request, as well as encouragement from the Baghdad-based Abbasid caliph, al-Mustanjid, who aimed to pressure Saladin in deposing his rival caliph, al-Adid. Saladin himself had been strengthening his hold on Egypt and widening his support base there. He began granting his family members high-ranking positions in the region; he ordered the construction of a college for the Maliki branch of Sunni Islam in the city, as well as one for the Shafi'i denomination to which he belonged in al-Fustat. After establishing himself in Egypt, Saladin launched a campaign against the Crusaders, besieging Darum in 1170. Amalric withdrew his Templar garrison from Gaza to assist him in defending Darum, but Saladin evaded their force and captured Gaza in 1187. In 1191 Saladin destroyed the fortifications in Gaza build by King Baldwin III for the Knights