Invasive grasses are widely acknowledged to alter fire regimes and threaten savanna ecosystems across northern Australia, yet little attention has focused on the threat this invasion poses to riparian habitats. Riparian habitats are a primary spread pathway of invasive grasses, providing highly suitable conditions for germination, establishment, and further spread of propagules. We document a case study of the spread and impacts of the high-biomass invasive grass, gamba grass (Andropogon gayanus Kunth) in riparian habitats of Litchfield National Park; an iconic protected area in northern Australia that contains significant natural, cultural and social values. We undertook helicopter-based surveys of gamba grass cover in 2014 and 2021-22. Surveys undertaken over 143,931 ha of the park, with gamba grass cover estimated over a five-point cover scale. Our survey showed that between 2014 and 2021-22 the gross infestation of gamba grass increased by 47%, to 29,712 ha. The percentage cover of gamba grass also substantially increased, with the number of grids cells with >50% gamba cover more than doubling in 7 years. This increase in gamba cover was particularly evident along riparian corridors and wetlands in the north-east, and south-west of the park. Our previous research has shown that compared to the average native grass fine fuel loads across northern Australia (~ 6 tha-1), the fuel loads associated with the highest gamba cover class can be between 16 – 25 tha-1. The increase in fuel loads in the park has fueled significant fire events in riparian vegetation, including one in August 2022 that burnt more than 12,000 ha of gamba grass, and resulted in helicopter evacuations of visitors camped in riparian areas of the park. Our study demonstrates the serious threat that gamba grass poses to riparian habitats in northern Australia, and highlights the urgent need for management to protect these critical habitats.