My thesis will be the first taxonomic revision of the fungal genus Marasmius in eastern Australia, examining species diversity, and placement of Australian taxa in a regional and global context. Applying systematic revisions from overseas studies (Wilson & Desjardin, 2005; de Oliveira 2020), I will revise descriptions of published taxa in two sections of the genus and publish 10-15 new species of Marasmius, using morphological, molecular data, and ecological criteria. Marasmius are important ecosystem saprotrophs, decomposing leaf litter, cycling nutrients and creating soil. While common tropical and subtropical fungi, they have been little studied in Australia. The species of this thesis, M. crinis-equi, M. elegans, M. haematocephalus and M. trichotus are thought to form complexes which require further phylogenetic analysis.