The mirid subfamily Orthotylinae is hyperdiverse in Australia but poorly described; this work is part of a series of papers on the documentation of this fauna. Two new species of the Australian endemic plant bug genus Myrtlemiris Cheng, Mututantri & Cassis (Heteroptera: Miridae: Orthotylinae: Orthotylini) are described as new to science: Myrtlemiris kararensis, sp. nov., and M. lochada, sp. nov. The new Australian genus and species Neomyrtlemiris picta gen. nov. et sp. nov. are also described. Myrtlemiris is analysed phylogenetically using 32 morphology-based characters, as well as molecular alignments (COI, 16S rRNA, 18S rRNA and 28S rRNA; including 1958 base pairs) with the genus found to be monophyletic based on molecular, morphological and combined analyses. Neomyrtlemiris is the sister to Myrtlemiris. Host plant association analysis demonstrated constraints to the myrtaceous tribe Chamelaucieae, with Malleostemon and Calytrix recovered as ancestral host plants. Ancestral state reconstructions were carried out on male genitalic structures, demonstrating the phylogenetic value of endosomal spicules. This work demonstrates that the Orthotylinae are a rich component of Australia’s biodiversity, particularly in the south-west of Western Australia.