Although studies have shown that urban environments and mass-transit systems have distinct genetic profiles, there are no systematic worldwide studies of these dense, human microbial ecosystems. To address this gap in knowledge, we created a global metagenomic and antimicrobial resistance (AMR) atlas of urban mass transit systems from 60 cities, spanning 4,728 samples and 4,424 taxonomically-defined microorganisms collected for three years. This atlas provides an annotated, geospatial profile of microbial strains, functional characteristics, antimicrobial resistance markers, and novel genetic elements, including 10,928 novel predicted viral species, 1302 novel bacteria, and 2 novel archaea. Urban microbiomes often resemble human commensal microbiomes from the skin and airways, but also contain a consistent "core" of 31 species which are predominantly not human commensal species. Samples show distinct microbial signatures which may be used to accurately predict properties of their city of origin including population, proximity to the coast, and taxonomic profile. These data also show that AMR density across cities varies by several orders of magnitude, including many AMRs present on plasmids with cosmopolitan distributions. Together, these results constitute a high-resolution, global metagenomic atlas, which enables the discovery of new genetic components of the built human environment, highlights potential forensic applications, and provides an essential first draft of the global AMR burden of the world's cities.### Competing Interest StatementThe authors have declared no competing interest.

Global Genetic Cartography of Urban Metagenomes and Anti-Microbial Resistance