A new Australian genus of Orthotylini, Xasmasoma, gen. nov. is described, with 12 new included species: X. acuminatus, sp. nov., X. agana, sp. nov., X. carrollae, sp. nov., X. celiae, sp. nov., X. chamelaucieaphila, sp. nov., X. mareeba, sp. nov., X. mimae, sp. nov., X. mungallala, sp. nov., X. nillinghoo, sp. nov., X. schuhi, sp. nov., X. silveirae, sp. nov. and X. woodstocki, sp. nov. These species were analysed phylogenetically using 25 morphology-based characters and molecular alignments (COI, 16S, 18S and 28S; 2096 base pairs), with the genus found to be monophyletic based on molecular, morphological and combined analyses. An analysis of host plant associations demonstrated no pattern of co-divergence and limited phylogenetic conservatism, aside from two subclades with respective Calytrix and Myrtaceae preferences. The biogeographic analysis revealed a south-western (South-west Interzone, Western Desert) area relationship, which is in distinction to the orthotyline genus Naranjakotta. The taxonomic component includes an identification key to species and diagnostic characters are illustrated, with detailed documentation of the male genitalia, and the genus uniquely possesses tile-like texture on the apex of the apophysis of the left paramere, and a single endosomal spicule.