born 786, Baghdad, Iraq
died August 833, Tarsus, Cilicia
Seventh caliph (r. 813–833) of the
He was the son of the celebrated Hārūn al-Rashīd and after his father's death (809) defeated his brother al-Amīn in a civil war (813) to assume the caliphate. Attempting to reconcile Sunnite and Shīʽite Muslims, he designated as his heir a Shīʽite, ʽAlī al-Riḍā, which failed to satisfy Shīʽite extremists and angered Sunnites. In any event, al-Maʾmūn was predeceased by his heir. He became a supporter of the {{link=Mutazilah">Mutazilite s, a theological school whose opinions on such issues as the nature of God and man's free will were at variance with accepted doctrine and found little popular support. His sponsorship of translations of Greek philosophical and scientific works and his building of observatories and libraries proved a more lasting legacy.