Sahara, (from Arabic ṣaḥrāʾ, “desert”) largest desert in the world. Filling nearly all of northern Africa, it measures approximately 3,000 miles (4,800 km) from east to west and between 800 and 1,200 miles from north to south and has a total area of some 3,320,000 square miles (8,600,000 square km); the actual area varies as the desert expands and contracts over time.