Originally nomads belonging to tribes of the Syrian or Arabian deserts but at the time of the Crusades the name used by Christians for all Muslims. In a surge of conquest Muslim Arabs swept into the Holy Land (western Palestine), north into the Byzantine territory of Asia Minor, and westward through North Africa during the 7th and 8th centuries. Spain was conquered (Moors), together with most of the islands in the Mediterranean; they held Sicily from the 9th to the 11th century. Their expansion was halted by the Carolingians in France only with great difficulty. The Crusades against them, though initially effective, did not prove decisive in the long term, and they were not finally expelled from Spain until the 15th century.

Within their conquered territories they had a profound effect on cultural life, particularly in architecture, philosophy, mathematics, and religion. In religion they were often tolerant of local beliefs and customs. The lurid accounts of Saracen bloodshed must be offset by the financial advantages of their presence: Saracen gold, used to pay for European goods, invigorated the Frankish economy.