Aristolochia quangnamensis T.V. Do (Aristolochiaceae), a new species from central Vietnam, is described and illustrated. It has a U-shaped perianth, a 3-lobed limb, and a 3-lobed gynostemium. Based on these characters it is placed in Aristolochia subgenus Siphisia. Morphologically, A. quangnamensis resembles A. annamensis, A. balansae, and A. tadungensis, but differs from them by having cream to yellowish-white, straight, narrowly funnel to cylindrically shaped upper tube, 2.2–2.8 cm long, densely pubescent outer surface, without striations or dots; a trumpet-shaped limb, with somewhat recurved margins of three limb lobes, a bright yellow inner surface, lacking verrucae and bristles, absence of annulus, and a bright yellow throat, without dots or striations.