Context Phytophthora cinnamomi Rands is a destructive pathogen of Australian native vegetation, often causing permanent damage to ecosystems and threatening the survival of rare, susceptible species. Despite that, much information about the effects of P. cinnamomi on plant species remains unpublished and the risk of extinction to most species is unknown. Aims We aimed to classify the risk of extinction from P. cinnamomi to Australian native plants. Methods We used available data and personal knowledge about P. cinnamomi effects on plants, spatial data on plant species distribution and habitat suitability of P. cinnamomi to assign an extinction-risk category of low, moderate, high or very high. Key results There are currently 65 plant species at a very high risk of extinction in Australia as a result of P. cinnamomi infection. The genera Andersonia, Banksia, Darwinia, Daviesia, Epacris, Gastrolobium, Grevillea, Hibbertia, Isopogon, Lambertia, Latrobea, Leucopogon, Phebalium and Styphelia have multiple species at a very high risk of extinction, most of which occur in south-western Western Australia. Conclusions The available data confirmed the high risk to the Australian flora from P. cinnamomi and identified species in plant families not previously known to be affected, highlighting data gaps (e.g. lack of knowledge about effects and risk in orchids and grasses). Implications Much more work is required to fully understand the risk from P. cinnamomi (and other Phytophthora species) to the Australian flora.