Umar ibn Abd al-Aziz — The Reforming Caliph
717–720 CE · The Umayyad Caliphate
Known by many scholars as the "fifth rightly-guided caliph" for his piety, justice, and reform. He returned stolen lands, abolished unjust taxes, ensured fair treatment of dhimmis (non-Muslim citizens), stopped the public cursing of Ali (RA) that had become standard in Umayyad mosques, and lived with extreme personal austerity despite ruling an empire.