The Pleurophyllum clade is one of two main clades within subtribe Celmisiinae (Astereae) and includes 10 species almost entirely restricted to New Zealand (one species also occurs in the Australian Macquarie Islands), with seven of them confined to Stewart Island/ Rakiura and the outlying Chatham and subantarctic islands. The clade is defined by its purple to dark red cyathiform disc corollas, which are absent from the other members of Celmisiinae. A new generic taxonomy of the clade is presented here with the recognition of three genera: Pleurophyllum with three species, Damnamenia (monotypic), and Macrolearia, a new genus segregated from Olearia, which is described here to accommodate the six species and one hybrid previously known as the “macrocephalous olearias.” The main morphological differences between the three genera lie in the growth form, trichome types of leaves and disc corollas, morphology of the style branches, presence/ absence of staminodes, and cypselae morphology. These morphological differences are also discussed within subtribe, tribe, and family contexts, and special consideration is given to the use of the “megaherb growth form” concept for Pleurophyllum. The allopatric distribution of the three recognized genera is also stressed. Seven new combinations: Macrolearia angustifolia, Macrolearia oporina, Macrolearia semidentata, Macrolearia chathamica, Macrolearia colensoi, Macrolearia lyallii, and Macrolearia × traillii, and five new synonyms are proposed, and four names are lectotypified. Taxonomic keys are provided for genera and species.