Deserts Antarctica is the largest desert. are regions that receive less than 250 mm (about 10 inches) of precipitation each year. By that definition of desert, at 14 million square kilometers (5.5 million square miles) Antarctica Antarctica is the largest desert. is the largest desert in the world. Going by the standard definition of “desert” (i.e both hot and dry) the Sahara desert is the largest desert. By the technical definition, however, the Sahara is the third largest, desert after the Antarctic and the Arctic deserts.