The world's largest desert is actually the very cold continent of Antarctica. It is the world's driest place, receiving less than two inches of precipitation annually. Antarctica is 5.5 million square miles (14,245,000 square kilometers) in area.utside of polar regions, Northern Africa's Sahara Desert is the world's largest desert at more than 3.5 million square miles (nine million square kilometers), which is slightly smaller that the size of the United States, the world's fourth largest country.