Two new species of the recently revised genus Oparanthus (Asteraceae, Subtribe Coreopsidinae) were discovered during the National Tropical Botanical Garden/Smithsonian Institution 1997 expedition to the Marquesas Islands. Oparanthus woodii W. L. Wagner & Lorence, sp. nov. is known from a single population on the island of Nuku Hiva, and O. tiva W. L. Wagner & Lorence, sp. nov. is known only from Tahuata. Small domatia with a tuft of hairs occur in O. tiva (and the previously known O. hivoanus), and similar but naked domatia are found occasionally in O. woodii. Domatia are of exceedingly rare occurrence in Asteraceae. Both new species are extremely rare and are considered critically endangered (CR) as are the other four species of the genus.