Hildegardia dauphinensis J. G. Zaborsky, a new species from southern Madagascar, is described and illustrated. Closely resembling Hildegardia perrieri (Hochr.) Arènes, it differs in having distinctive multi-branched stellate hairs on the calyces and leaves, and in having flat (not revolute) leaf blades. Known only from the type specimen collected near Fort Dauphin, it is Critically Endangered. A key to the four Malagasy species of Hildegardia Schott & Endl. is also presented.