The genus Lithophyllum (Lithophylloideae, Corallinaceae, Rhodophyta) is represented by six species in south-eastern Australia L. chamberlainianum Woelkerling & Campbell, L. corallinae (Crouan & Crouan) Heydrich, L. cuneatum Keats, L. pustulatum (Lamouroux) Foslie, L. riosmenae, sp. nov., and L. stictaeforme (Areschoug in Agardh) Hauck. Four of these taxa are commonly found in Australia, whereas L. cuneatum was previously known only from Fiji and L. riosmenae is newly described. Morphological and anatomical accounts are provided, including keys, information on distribution, nomenclature and habitat in south-eastern Australia. South-eastern Australian species are primarily delimited on characters relating to tetrasporangial conceptacles and the presence/absence of a semi-endophytic habit. Ten species of Lithophyllum are now confirmed to occur in Australia and their diagnostic characters are detailed. Confirmed Australian species of Lithophyllum are primarily delimited on characters relating to tetrasporangial conceptacles, the presence/absence of a semi-endophytic habit and the growth-form. Biogeographic comparisons between south-eastern Australia and other Australian biogeographic regions are also made. Eight species of Lithophyllum are known to occur in southern Australia, three in tropical eastern Australia and three in subtropical western Australia. Southern and south-eastern Australia show major overlap, with five species occurring in both regions. L. pustulatum and L. stictaeformae are widely distributed, having been confirmed to occur in eastern tropical, western subtropical, warm temperate and cold temperate waters within Australia.