The Sahara is the world’s largest hot desert and one of the harshest environments on the planet. It is third largest desert overall after Antarctica and the Arctic, which are cold deserts. At 3.6 million square miles (9.4 million square kilometers) bigger than the entire USA! The desert covers 11countries (large sections of Algeria, Chad, Egypt, Libya, Mali, Mauritania, Morocco, Niger, Western Sahara, Sudan and Tunisia).