Primulina hoangmongii, a new species from Yen Bai Province of northern Vietnam, is described and illustrated. It is similar to P. albicalyx in its robust rhizome, rosette leaves, and yellow flowers. However, P. hoangmongii is clearly distinguished by its linear to narrowly-lanceolate bracts, 8–12 × 2–3 mm (vs. narrowly ovate to ovate, 18–25 × 9–14 mm), green calyx (vs. white), rich yellow corolla (vs. pale yellowish), base of the upper lip flat, thin and rich pure yellow (vs. swelling between lobes, yellow-brownish), and a ligulate, entire stigma (vs. deltoid, 2-lobed). The conservation status of P. hoangmongii is preliminarily assessed according to IUCN criteria as Critically Endangered (CR).

plant diversity, endemism, plants of limestone karst, plant taxonomy, Eudicots