The least populated places in the world are the alpine regions, deserts, and polar regions, in descending order of population. Some other regions, such as thick rainforest or eastern Russia are also among the least populated places, with an average population of one person per ten square kilometers or less. The world's least populous nation is Greenland, which is two million square kilometers in size and has a population of just 60,000, making its average population density just one person per 40 square kilometers.
Every continent except Europe has large desert and rainforest regions that are among the least populated places outside of Antarctica. The world's largest deserts include the Sahara Desert of Africa, the Atacama Desert of Chile, the Arabian Desert of Saudi Arabia, the Gobi Desert of China, and the Western Australian Desert in Australia. Large, sparsely populated rainforest regions include the Amazon Rainforest of Brazil, which has a few tribes that have never experienced contact with the outside world; the Borneo Rainforest of Indonesia, which also has isolated tribes; and the Congo Rainforest of Africa, which lies deep within the heart of Africa.
The least populated places associated with polar climates include most of Canada, Greenland, and Siberia. These regions are extremely cold and are mostly populated by native tribes and people prospecting for oil and minerals. The permafrost means that all water pipes must go above ground, otherwise they'd freeze solid, and at the most extreme latitudes, there is a polar treeline which means that no trees will even grow. This is hardly a hospitable climate, and these regions are populated accordingly.
The single least populated place on Earth is the huge land of Antarctica, the world's southernmost, coldest, windiest, and driest continent. This polar wasteland only has about 4,000 visitors during the summer, just 1,000 during the winter, and no permanent residents. During the winter, the average population density is just one person per 14,400 square kilometers. Most of the Antarctic Plateau is an entirely featureless landscape devoid of life, even at the bacterial level.