The Western Desert covers an area of some 700,000 km², thereby accounting for around two-thirds of Egypt's total land area. This immense desert to the west of the Nile spans the area from the Mediterranean Sea southwards to the Sudanese border. The desert's Jilf al Kabir Plateau, at a mean altitude of some 1000m, constitutes an exception to the uninterrupted territory of basement rocks covered by layers of horizontally bedded sediments forming a massive plain or low plateau. The Great Sand Sea lies within the desert's plain and extends from the Siwa Oasis to Jilf al kabir. Escarpments (ridges) and deep depressions (basins) exist in several parts of the Western Desert, and no rivers or streams drain into or out of the area.

The other major Oases form a topographic chain of basins extending from the Faiyum Oasis (sometimes called the Fayyum Depression) which lies 60 kilometers (37 mi) southwest of Cairo, south to the Bahariya, Farafrah, and Dakhlah oases before reaching the country's largest oasis, Kharjah. A brackish lake, birket Qarun, at the northern reaches of Al Fayyum Oasis, drained into the Nile in ancient times. For centuries sweetwater artesian Wells in the Fayyum Oasis have permitted extensive cultivation in an irrigated area that extends over 1,800 square kilometers (695 sq mi).