Bidens meyeri (Asteraceae/Compositae) is described and illustrated from Rapa, Austral Islands, (French Polynesia). This new species is presumed to be most closely related to Bidens saint-johniana from nearby Marotiri Island. Bidens meyeri may be distinguished from B. saint-johniana based on the length of the peduncle (3 cm versus 10 cm), apex of the inner involucral bracts (glabrous vs. puberulent), smaller leaves (2.0–2.3 cm vs. 5–6 cm), and the general smaller size of the new species. Known from less than 50 individuals and restricted to one remote location, Bidens meyeri falls into the IUCN Critically Endangered (CR) category. The new species is named in honor of Dr. Jean-Yves Meyer, Délégation à la Recherche, Polynésie Française,