The spread of high pathogenicity avian influenza virus (HPAIV) H5N1 clade 2.3.4.4b into Antarctica represents a major threat to polar wildlife. Here we report on the detection and genomic analysis of HPAIV H5N1 in a kelp gull (Larus domincanus), a pintado petrel (Daption capense), and an Antarctic fur seal (Arctocephalus gazella) during the 2023/2024 and 2024/2025 austral summers in the South Shetland Islands, Antarctica. Whole-genome sequencing and phylogenetic analysis revealed that the viruses from each of these three hosts descended from a different introduction event. The gull and fur seal strains clustered with viruses that had been previously detected predominantly in marine mammals in South America, while the petrel strain clustered with viruses detected in seabirds and marine mammals in the Subantarctic island of South Georgia. These findings reveal there is extensive epidemiological connectivity between South America and Antarctica, with South Georgia also serving as a “stepping stone” for virus spread in the region. The dissemination of HPAIV H5N1 in Antarctic wildlife highlights the urgent need for enhanced surveillance, strict biosafety protocols, and a One Health approach to prevent further spread and ecological disruption in one of the planet’s most vulnerable environments.