Abu Muhammad Musa ibn Mahdi al-Hadi(Arabic: أبو محمد موسى بن المهدي الهادي‎) (born: 147 AH [764 AD]; died: 170 AH [786 AD]) was the fourth Abbasid caliph who succeeded his father Al-Mahdi and ruled from 169 AH (785 AD) until his death in 170 AH (786 AD).Al-Hadi was the eldest son of Al-Mahdi and Al-Khayzuran and like his father he was very open to the people of his empire and allowed citizens to visit him in the palace at Baghdad to address him.