Background and aims: The human gut is home to a largely underexplored microbiome component, the archaeome. Little is known of the impact of geography, urbanization, ethnicity, and diet on the gut archaeome in association with host health. We aim to delineate the variation of the human gut archaeome in healthy individuals and its association with environmental factors and host homeostasis. Methods: Using metagenomic sequencing, we characterized the fecal archaeomes of 792 healthy adult subjects from 5 regions in China, spanning 6 ethnicities (Han, Zang, Miao, Bai, Dai, and Hani), consisting of both urban and rural residents for each ethnicity. In addition, we sampled 119 host variables (including lifestyle, diet, and blood parameters) and interrogated the influences of those factors, individually and combined, on gut archaeome variations. Results: Population geography had the strongest impact on the gut archaeome composition, followed by urbanization, dietary habit, and ethnicity. Overall, the metadata had a cumulative effect size of 11.0% on gut archaeome variation. Urbanization decreased both the alpha-diversity (intrinsic microbial diversity) and the beta-diversity (inter-individual dissimilarities) of the gut archaeome, and the archaea-to-bacteria ratios in feces, whereas rural residents were enriched for Methanobrevibacter smithii in feces. Consumption of buttered milk tea (a characteristic diet of the rural Zang population) was associated with increased abundance of M. smithii. M. smithii was at the central hub of archaeal-bacterial interactions in the gut microecology, where it was positively correlated with the abundances of a multitude of short chain fatty acid (SCFA)-producing bacteria (including Roseburia faecis, Collinsella aerofaciens, and Prevotella copri). Moreover, a decreased abundance of M. smithii was associated with increased human blood levels of cholinesterase in the urban population, coinciding with the increasing prevalence of noncommunicable diseases (such as dementia) during urbanization. Conclusions: Our data highlight marked contributions of environmental and host factors (geography, urbanization, ethnicity, and habitual diets) to gut archaeome variations across healthy individuals, and underscore the impact of urbanization on the gut archaeome in association with host health in modern society.