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The polar regions, comprising the Antarctic, Arctic and Tibetan Plateau, represent the most extreme environments on Earth. Soils across the polar regions harbor diverse microorganisms, which dominate the biogeochemical cycling. However, polar soil microbial diversity is largely underrepresented, and has not been directly compared with the non-polar regions at a global scale, which hinders our understanding of the potential importance of polar microbial diversity. In this study, we investigated the global microbial diversity and taxonomy by comparing 1114 soils, derived from the Antarctic (203), Arctic (432), Tibetan Plateau (104) and non-polar regions (375) across all continents. Soil microbial diversity was found to increase gradually from the Antarctic < Arctic < Tibetan Plateau and < non-polar regions. Soil microbial diversity dominantly corresponded to mean summer temperature in the polar regions and to soil pH in non-polar regions, respectively. Soil microbial community structure significantly differed across the different biogeographical regions, while the Antarctic exhibited the highest habitat-specificity. Over 26,000 phylotypes were observed across global soils, of which 21.8% were unique to the three poles, and 21.2% were apparently ubiquitous globally. Polar soils were dominated by fewer phylotypes, but individual phylotype showed greater dominance than that in non-polar regions. Our study reveals unique patterns of soil microbial diversity and taxonomic compositions in polar regions, and highlights the importance of environmental stresses in controlling soil microbial community. [Display omitted] • Polar soil microbial diversity (SMD) was compared with global non-polar regions. • 21% of the phylotypes were globally ubiquitous, 22% were three-poles specific. • Actinobacteria was the most ubiquitous, Firmicutes was predominately endemic. • SMD corresponded to summer temperature in poles and to soil pH in non-poles. • Polar soils were dominated by fewer microbial phylotypes with greater dominance. [ABSTRACT FROM AUTHOR]