Abstract Molecular analyses of >80 specimens of foliose Bangiales from the coasts of Taiwan reveal that only two species are present: Pyropia acanthophora and Pyropia haitanensis. These species had been previously identified as Pyropia suborbiculata (obovoid form), Porphyra yamadae (crisped form), and Pyropia dentata (ribbon-like form) based on morphology. Populations previously identified as P. yamadae from Taiwan and those from the type locality of this species (Ojika Island, Nagasaki Prefecture, Japan) are genetically identical to Py. acanthophora and should be treated as a later synonym of Py. acanthophora, a species originally described from Brazil. Thalli with obovoid blades from northeastern Taiwan that resemble Py. suborbiculata and those with lanceolate or linear blades from Penghu Archipelago that resemble Py. dentata are also genetically identical to Py. acanthophora. In contrast to the widespread Py. acanthophora, Py. haitanensis (previously misidentified as Py. dentata) was found only at two sites, both in Keelung City. Among the nine cox1 haplotypes of Py. acanthophora identified worldwide, eight are present in Taiwan. At least five out of the eight cox1 haplotypes are present in populations from the eastern coast of Keelung City. The high level of genetic diversity within a single species supports the need for establishment of a marine ecological area in this region.