The Western Desert covers about 700,000 square kilometers (equivalent in size to Texas) and accounts for about two-thirds of Egypt's land area. This immense desert to the west of the Nile spans the area from the Mediterranean Sea south to the Sudanese border. The desert's Jilf al Kabir Plateau has an altitudÍÍÍÍe of about 1,000 meters, 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 Siwah Oasis to Jilf al Kabir. Scarps (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 government has considered the Western Desert a frontier region and has divided it into two governorates at about the twenty-eighth parallel: Matruh to the north and New Valley (Al Wadi al Jadid) to the south. There are seven important depressions in the Western Desert, and all are considered oases except the largest, Qattara, the water of which is salty. The Qattara Depression is approximately 15,000 square kilometers (about the size of Connecticut and Rhode Island) and is largely below sea level (its lowest point is 133 meters below sea level). Badlands, salt marshes, and salt lakes cover the sparsely inhabited Qattara Depression.

Limited agricultural production, the presence of some natural resources, and permanent settlements are found in the other six depressions, all of which have fresh water provided by the Nile or by local groundwater. The Siwah Oasis, close to the Libyan border and west of Qattara, is isolated from the rest of Egypt but has sustained life since ancient times. The Siwa's cliff-hung Temple of Amun was renowned for its oracles for more than 1,000 years. Herodotus and Alexander the Great were among the many illustrious people who visited the temple in the pre-Christian era.

The other major oases form a topographic chain of basins extending from the Al Fayyum Oasis (sometimes called the Fayyum Depression) which lies sixty kilometers southwest of Cairo, south to the Bahriyah, Farafirah, and Dakhilah oases before reaching the country's largest oasis, Kharijah. A brackish lake, Birkat 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.

Data as of December 1990