Analysis of Google Earth imagery shows that barchans have an uneven global distribution. Nevertheless, they are widespread, and found in many of the world’s deserts, as well as from some moist coastal areas. Most barchans occur in 11 main provinces, and some of these are great in extent and contain large numbers of individual dunes. These provinces are: Egypt and the Sudan, Namib, Peru, Somalia, Western Sahara, Iraq/Iran border, Baluchistan and Seistan, Eastern Arabia, Central Sahara, Mauritania, and the Hexi Corridor and neighbouring parts of China and Mongolia. While there is considerable variability of individual barchan dimensions in any one area, mean widths of barchans also vary substantially. The mean of means for all 54 locations is 121 m. Wind directional variability is a major control of their distribution, with nearly all locations having an index of directional variability between 0.7 and 0.97. Most barchans occur in dry locations, where vegetation cover is likely to be low, and with mean annual rainfall totals below 100 mm. A range of other controls account for barchan distribution at a variety of scales, including their location with regard to sand seas. Barchans occur in two main areas (1) on the margins of sand seas, and (2) in sand transport corridors linking sand source zones and depositional areas, especially downwind from source zones. It is also evident that barchans are present where sand is channeled along wind-fluted furrows or pours down gaps in escarpments and plateaux. Sand supply is an important control of their distribution.