The first monographic account of the south-eastern Australian representatives of the Corallinaceae, subfamily Mastophoroideae (Corallinales, Rhodophyta) is presented. The Mastophoroideae contains eight extant genera, four of which [Hydrolithon, Mastophora, Neogoniolithon, Pneophyllum] were confirmed to occur in south-eastern Australia. Hydrolithon is represented by six species (H. farinosum, H. improcerum, H. munitum, H. onkodes, H. rupestre and H. samoënse). Pneophyllum is represented by three species (P. coronatum, P. fragile and P. submersiporum) while Mastophora and Neogoniolithon are represented by a single species each (Mastophora pacifica and Neogoniolithon brassica-florida). Morphological and anatomical accounts are provided, including keys to genera and species, comparisons with related south-eastern Australian mastophoroid species, information on distribution, seasonality, habitat and nomenclature. Brief biogeographical comparisons between south-eastern Australia and other Australasian regions are also made.