What is the largest desert on Earth, including polar deserts?

The Antarctic Desert is the largest desert on Earth when polar deserts are included.

A desert is defined primarily by very low precipitation, not by heat or the presence of sand. Antarctica qualifies as a polar or cold desert because its frigid atmosphere holds little moisture and much of the continent receives very little annual snowfall. Its immense ice-covered area therefore counts as desert terrain.

The Antarctic Desert covers roughly 14.2 million square kilometres, making it larger than the Arctic Desert and far larger than the Sahara. About 98% of Antarctica is covered by a thick continental ice sheet, while the remainder consists largely of exposed rock and other ice-free terrain.

The answer often surprises people because “desert” commonly evokes hot, sandy landscapes. The Sahara is the world’s largest hot desert, but it is not the largest desert overall. Antarctica’s McMurdo Dry Valleys offer an especially stark example of polar aridity: some valleys receive almost no snow and contain extremely dry, rocky landscapes shaped by powerful katabatic winds.