Abstract <p>Integrating human, animal, and environmental health is crucial for combating infectious diseases, as an estimated 60 to 75% of emerging infectious diseases originate from zoonotic sources globally. In this study, we analysed 1274 shotgun metagenomic faecal samples of humans, pigs, and chickens collected across multiple countries to estimate levels of microbial sharing at the species-level genome bins (SGBs) resolution. We confirm that host species, rather than geography, significantly structures the gut microbial community, as shown by alpha and beta diversity analyses. Despite this high host specificity, we identified substantial cross-host sharing of SGBs, including taxa recognised as pathogens such as <i>Escherichia coli</i>, <i>Clostridium perfringens</i>, <i>Clostridium innocuum</i>, <i>Clostridium disporicum</i>, <i>Enterococcus</i> species, and<i> Streptococcus alactolyticus.</i> Core taxa were predominantly host-specific, while non-core taxa were more frequently shared across humans, pigs, and chickens. LEfSe analysis identified distinctive microbial signatures for each host, further supporting differences in community composition. These findings demonstrate that unrelated and geographically distant humans and livestock can harbour highly similar microbial populations with pathogenic potential. This work provides molecular evidence supporting the need for integrated One Health surveillance to better detect, manage, and prevent zoonotic and reverse zoonotic transmission events across interconnected human, animal, and environmental systems.</p> Key points <p>•&#xa0;<i>There is substantial cross-host sharing of species-level genome bins, including potential pathogens</i></p> <p>•&#xa0;<i>Core taxa are predominantly </i><i>host-specific</i></p> <p>•&#xa0;<i>Non-core taxa are more likely to be shared across humans, pigs, and chickens</i></p>