Abbas Ben Abd-El-Mottalib, paternal uncle of Mohammed, born at Mecca in 566, died in 652. He was the progenitor of the Abbasside dynasty, but not known as such until an adventurer, requiring a title to his usurpations, traced his descent to him. He was only four years the senior of Mohammed, and was yet a pagan when the prophet commenced his religious career, and long hesitated to espouse his nephew's cause. In the battle at the well of Bedr Abbas fought against his nephew, and was taken prisoner. So soon, however, as Mohammed's career seemed prosperous, the uncle gave in his adhesion, and became one of the most zealous supporters of the new faith. His influence and mediation brought over the family of the Koreishites; for when Mohammed, at the head of a powerful force, was about laying siege to Mecca, Abbas went forward, and not only demonstrated to Abu Sofian the inutility of resistance, but induced him to come to Mohammed's camp and to have a personal interview, which ended in Abu Sofian's making the profession of faith on behalf of himself and his kinsmen. When Mecca surrendered to Mohammed, the holy well Zemzem was retained, in deference to Abbas, its keeper, though other pagan rites and superstitions were swept away.

At the battle of Honeïn Abbas rallied the fugitives and recovered the fortune of the day. At Mohammed's funeral he was chief mourner. Caliph Omar, on occasion of a terrible drought, took his hand, and prayed to Allah by the virtues of Abbas to have pity on the perishing people. Caliph Othman also, when he met the patriarch, dismounted.