Gypsum crusts are a significant pedologic and geomorphic feature in many warm semi-arid areas yet they are rarely described in detail. This review relies heavily on information from north Africa and to some extent south-west Africa though literature from other areas is also examined. A brief summary of different classifications of gypsum crust types is followed by a discussion of their world-wide distribution and the nature of the various forms. A number of the possible processes of gypsum crust formation are examined and the data on the ages of crusts are summarized. Keywords: Namibia, Namib Desert, Kuiseb River, Swakop River, Tunisia, desert geomorphology, arid environment, crust formation, weathering, calcretes, gypsum substrate, aeolian bedforms, aeolian sedimentation, landform evolution, landform geology, geochemistry.