The mostly uninhabited southern half of the province is covered by the Grand Erg Oriental, a vast region of uninterrupted sand dunes.
The northern half of the province is a mixture of sandy desert with scarce vegetation, scattered oases, and salt lakes.
The most notable oases are the Oued Souf region, upon which the capital El Oued and neighbouring towns are built, as well as oases located near the towns of El M'Ghair and Djamaa, both of which support extensive palm plantations.
These salt lakes, and the surrounding areas, lie as much as 30 metres (98 ft) below sea level; nearby towns and villages including Hamraia, Méguibra, Dendouga and Aïn Cheikh are also below sea level.
Precipitation is very low throughout the province, but somewhat more rain does fall in the north, particularly during the winter and adjacent months.