Ommiyades, the second dynasty of oriental caliphs, beginning with Moawiyah, the son of Abu Sofian, in 661, and continuing until 750. They derived their name from Ommiyah, an ancestor of Moawiyah. The latter had during the lifetime of Ali, the fourth caliph of the first or Arabian dynasty, made himself master of Syria and Egypt, and after the assassination of Ali gained possession of the whole empire, through the abdication of his successor Hassan. The office of caliph now became hereditary in the family of this monarch, and so continued until the defeat and death of Mer-wan II., the 14th sovereign of the line (750). During the sway of this dynasty, Turkistan, Spain, and Georgia were conquered. But the progress of the Moslem arms was retarded by constant civil dissensions, and in Europe their conquests were effectually stayed by their defeat on the plains of Poitiers (732). After the contest between Merwan II. and Abul Abbas had ended in the defeat of the former, Abdullah, an uncle of Abul Abbas, called a meeting of the Ommiyades, and treacherously massacred them all but two.
One of these fled to Arabia, where his descendants ruled as late as the 16th century; and the other escaped to Mauritania, whence he was called to Spain, and founded the kingdom and subsequent caliphate of Cordova as Abderrahman I. (See Caliph).