Leadbeater's possum (Gymnobelideus leadbeateri) is an arboreal marsupial that occurs primarily in the montane ash forests of the Central Highlands of Victoria. Leadbeater's possum is among the best studied endangered species globally. Despite extensive monitoring and research, the ongoing population trajectory of the species has resulted in its recent upgrading from Endangered to Critically Endangered. One of the key processes threatening the species is the widespread use of clearfell logging, which significantly degrades the habitat of the species and results in long-term habitat loss, fragmented populations, and an elevated risk of high-severity crown-scorching fires. A general principle underpinning conservation biology is to remove key threatening processes to enhance the conservation of species. The cessation of clearfell logging and a major expansion of the reserve system are urgently needed to limit the risk of extinction of Leadbeater's possum. Current government policies and practices that continue to result in clearfelling of montane ash forests run counter to the large body of science indicating what is needed to conserve Leadbeater's possum. A large ecological reserve is urgently required to maximise the chances that the species will persist in the wild.