Since 2020, H5Nx high pathogenicity avian influenza viruses (HPAIVs) have caused widespread disruptions not only to global agriculture and trade but also to the health of free-ranging wildlife. Pinnipeds have experienced greater mortality from H5Nx HPAIV than any other mammalian taxa. Emergent virus strains, persisting over long time periods and vast geographic distances, have repeatedly triggered large-scale mortality events in pinniped populations. Of particular concern is the spread of H5Nx HPAIV to the Southern Hemisphere-including the emergence of a marine mammal-adapted clade in South America and detections in the sub-Antarctic and Antarctic-and to other remote locations such as the Hawaiian Islands. These developments elevate concern for the world´s endangered, isolated and endemic pinnipeds. While managing HPAIV in any animal population is a formidable task, working with free-ranging marine mammals poses unique challenges. In this review and perspective piece, we attempt to synthesize complexities at this intersection. We describe lessons learned from HPAIV investigations in marine wildlife, highlight gaps in knowledge and capacity, and discuss the incorporation of outbreak risk assessment and countermeasures into pinniped conservation. Finally, we propose ways in which pinnipeds-and marine wildlife broadly-could be better integrated into existing systems for HPAIV intelligence, control and prevention. This article is part of the theme issue ´Managing infectious marine diseases in wild populations´.