The highly pathogenic avian influenza (HPAI) virus H5N1 is currently spreading worldwide, with Oceania remaining the only continent largely unaffected until recently, when positive cases in migratory birds were detected in Western Australia and South Australia, and, more recently, a suspected case in New South Wales. Furthermore, H5N1 in Heard Island has caused widespread mortality in elephant seal pups. Migratory waterfowl and shorebirds, recognised as key vectors of avian influenza viruses (AIV), connect Australia with global transmission networks. Here, we developed an agent-based model to predict the spread of H5N1 following potential incursions across different regions of Australia. Our results suggest that the incursion region strongly affects outbreak spread and duration. The spread of H5N1 in Australia creates a substantial risk for poultry outbreaks and potential spillover into wildlife populations, particularly in ecologically sensitive breeding areas. These findings provide critical insights for informing national preparedness, guiding targeted surveillance, and strengthening One Health strategies to mitigate the impact of HPAI in Australia.