Austropaxillus is a genus of fungi in the family Serpulaceae, containing nine species found in Australia, New Zealand and South America.

[1] Later analysis revealed a relationship to Gymnopaxillus, a small genus of truffle-like fungi known from south-eastern Australia, Argentina, and Chile.

[2] Austropaxillus and Gymnopaxillus, both mycorrhizal genera, form a monophyletic clade that is sister to the saprotrophic genus Serpula.

Using molecular clock analysis, the split between Austropaxillus and Serpula has been estimated to have occurred about 34.9 mya, roughly coinciding with the separation of South America and Australia from Antarctica.

[5] Morphologically, the fruit bodies of these fungi resemble those of Paxillus, namely they have funnel-shaped caps with inrolled margins and decurrent gills.