The crab spiders of the genus Diaea from Australia are revised. All the known 30 species are redescribed and illustrated. The type species of the genus — Diaea dorsata (Fabricius, 1777) (distributed in Palaearctic) is also included into this study. All the former members of Diaea from Australia changed their taxonomic position as a result of transfer to other genera. Three new genera were established: Australomisidia gen. nov., Boomerangia gen. nov. and Lehtinelagia gen. nov. Twenty new combinations are proposed: Australomisidia cruentata (L. Koch, 1874), A. elegans (L. Koch, 1876), A. ergandros (Evans, 1995), A. inornata (L. Koch, 1876), A. kangarooblaszaki (Szymkowiak, 2008), A. pilula (L. Koch, 1867), A. rosea (L. Koch, 1875), A. socialis (Main, 1988), Boomerangia dimidiata (L. Koch, 1867), Cetratus caecutiens (L. Koch, 1876), C. circumlitus (L. Koch, 1876), C. rubropunctatus (Rainbow, 1920), C. tenuis (L. Koch, 1875), Lehtinelagia evanida (L. Koch, 1876), L. multopunctata (L. Koch, 1874), L. prasina (L. Koch, 1876), L. pulleinei (Rainbow, 1915), L. variabilis (L. Koch, 1875), Runcinia insecta (L. Koch, 1875), Zygometis xanthogaster (L. Koch, 1875). Four species are regarded as nomina dubia: D. mollis L. Koch, 1875, Diaea olivacea L. Koch, 1875, D. plumbea L. Koch, 1875, D. punctipes L. Koch, 1875. Following specific names are synonymised: Diaea blanda L. Koch, 1875 with Australomisidia pilula, Diaea haematodactyla L. Koch, 1875 with Lehtinelagia evanida, Diaea jucunda Thorell, 1881 with Mastira adusta (L. Koch, 1867), Diaea multimaculata Rainbow, 1904, Diaea punctata L. Koch, 1875 with Lehtinelagia multopunctata, Diaea velata L. Koch, 1876 with Boomerangia dimidiata, Misumena tristania Rainbow, 1900, M. lactea L. Koch, 1876 with Diaea xanthogaster L. Koch, 1875 (and transferred to the genus Zygometis), Runcinia affinis Simon, 1897 with Diaea insecta L. Koch, 1875 (placed into Runcinia) and Xysticus bilimbatus L. Koch, 1875 with Australomisidia cruentata. Diaea elegans L. Koch, 1876 was removed from synonyms of D. cruentata and reinstaled. Lectotypes are designated for 11 species: Australomisidia cruentata, A. elegans, A. pilula, A. rosea, Cetratus caecutiens, C. rubropunctatus, Lehtinelagia evanida, L. multopunctata, L. prasina, L. variabilis, Runcinia insecta. Identification keys for Australian species of genera Australomisidia, Cetratus and Lehtinelagia are provided. Maps with collection localities for discussed species are given and their distributional patterns are analysed. The original number of 30 species of Diaea from Australia which are subject to the revision is reduced to 21; among them 17 (80%) are endemic to Australia. The phylogeny reconstruction based on the nucleotide sequences of the fragment of the gene of mitochondrial cytochrome oxidase subunit I (COI, mtDNA) are presented. Tree of Australian “Diaea” includes two main phylogenetic lineages: Thomisinae (15 species) and Dietinae (3 species). The results of the sequence analysis justify the proposed taxonomic changes.