AbstractOstrea aupourian.sp., possibly the only representative of its genus in New Zealand, is described. The oyster is small, largely adherent to the substrate, and occurs in the lower tidal zone of northern New Zealand. It is incubatory and has an extensive breeding period and a characteristic planktonic larva. Re‐examination of the holotype ofO. fococarensFinlay, 1928, and similarly identified specimens in Suter's collection, has revealed significant differences from the new oyster and true relationships withTiostrea lutaria(Hutton, 1873).