Antarctica is the largest desert on Earth by total area. A desert is defined by very low precipitation, not by heat, and the Antarctic interior receives so little snowfall that it qualifies as a polar desert.
Antarctica covers about 14 million square kilometres, making its desert area substantially larger than the Sahara. The continent’s extremely cold air holds little water vapour, while powerful winds and high elevation further limit effective moisture. Much of the snow and ice accumulated there remains for very long periods because melting is uncommon across the interior.
The Sahara is the world’s largest hot desert, covering roughly 9.2 million square kilometres across northern Africa. This distinction explains why many people answer the Sahara when asked for the largest desert. Antarctica also contains the largest ice sheet on Earth, but “desert” and “ice sheet” describe different characteristics: one concerns precipitation, while the other concerns stored frozen water.