The current paper presents molecular data from three chloroplast markers (atpB–rbcL spacer, trnG G2 intron, trnL–trnF intron and spacer); morphological data, and geographic data to support the recognition of nine species belonging to Radula subg. Odontoradula in Australasia. R. ocellata, the subgeneric type from the Wet Tropics bioregion, is maintained as distinct from its sister species, R. pulchella, from south-eastern Australian rainforests; both species are Australian endemics. Reinstatement of R. allisonii from synonymy, under R. retroflexa, is supported by molecular data and morphological characters, including the absence of triradiate trigones on leaf-lobe cell walls, the apex of lobules on primary shoots not being turned outwards, the oblong-elliptic female bracts, and the perianths having a pronounced wing. Reinstatement of R. weymouthiana, from synonymy under R. retroflexa, is also supported by molecular data and morphological characters, including the presence of a single low dome-shaped papilla over each leaf-lobe cell, and the large imbricate lobules on primary shoots. R. weymouthiana occurs in Tasmania and New Zealand, whereas R. allisonii is a New Zealand endemic. Australian R. retroflexa exhibits differentiation into epiphytic and rheophytic morphs, interpreted as ecotypes. Australian individuals, comprising both epiphytic and rheophytic morphs, are monophyletic and nested within a clade containing individuals from other regions. R. novae-hollandiae is newly reported for the New Zealand Botanical Region, from Raoul Island in the Kermadecs. R. novae-hollandiae exhibits decoupling of morphological and molecular divergence, with Australian individuals forming two clades reflecting geography (a Wet Tropics bioregion clade and a south-eastern Rainforest clade). These clades exhibit equivalent levels of molecular divergence, as observed in R. pulchella and R. ocellata, but no morphological differences. Similar levels of molecular divergence were observed in trans-Tasman populations of R. tasmanica. The New Zealand endemic, R. plicata, is excluded from the Australian flora, and R. cuspidata replaces R. dentifolia for the New Zealand endemic species formerly known by both names.