Six species of Marthamyces are reported for Australia. Three of the species are described as new, the others had previously been reported from Australia as species in the genera Propolis and Naemacyclus. Most of the Australian species are host-specialised: M. emarginatus is known only from Eucalyptus, M. gilvus from Cyperaceae, M. hakeae from Hakea, and M. oritis from Orites. Marthamyces barbatus, common on Eucalyptus, is known also from a single collection on Richea. Marthamyces quadrifida, although known from only a few Australian collections, is a widespread tropical species and is likely to be common on a range of hosts in northern Australia. All species are described and illustrated, and a key to the Australian Marthamyces species is provided.