Al-Salman Depression is one of the largest karst forms in the Southern Desert of Iraq. It is of doline type, being formed in carbonates of Dammam Formation of Eocene age. The length of the depression is 20 Km, whereas, the width is variable, it is (6.5, 10 and 4.5) Km, in the northern, central and southern parts, respectively, whereas, the depth ranges from (5 – 35) m.The Iraqi Southern Desert is one of the most extensive karstified areas in Iraq. Different types and forms of karst were developed with different sizes. Among the karst forms is Al-Salman Depression. The main reason of karstification is the presence of the carbonates of the Dammam Formation, which are underlain by the Rus Formation (Early Eocene); it consists mainly of anhydrite with limestone interlayers. The Pleistocene Period witnessed wet climate in the studied area, which had contributed in the karstification of the Iraqi Southern Desert, in which karst forms have played a big role in development of special landscape, which is characterized by special drainage system and enormous amount of closed depressions and blind valleys. Originally, Al-Salman Depression was consisting of three main depressions, which merged together due to karstification, head ward erosion and collapsing parts of the rims. The presence of the sediments of Zahra Formation (Pliocene – Pleistocene) in the Salman Depression indicates Pliocene and most probably uppermost Late Miocene age for the depression that has developed due to karstification and collapsing, which are still active processes. This age and genesis hold good for all those large depressions in the Iraqi Southern Desert.