Hedyotis konhanungensis B.H.Quang, T.A.Le, K.S.Nguyen & Neupane (Rubiaceae, Spermacoceae), a new species from Vietnam, is described and illustrated based on morphological and phylogenetic evidence. The new species is morphologically distinct from all southeastern Asian Hedyotis L. in its set of morphological traits such as the leaf type (shape and thickness), growth habit, and floral parts (color of inflorescence axis and the shape of calyx lobes). This species shows similarities with Hedyotis shenzhenensis, H. shiuyingiae and H. yangchunensis from China in habit, leaf blades, floral bracts, dichasial cymes, and fruits, but it is phylogenetically distinct and can be distinguished from them by the following combination of characteristics; cylindrical or subterete stem up to 15 cm tall, obovate to oval leaves spreading along the stem, broadly ovate or deltoid stipules with an entire margin and cuspidate apex, suborbicular or broadly oval lowest floral bracts, ovate or nearly oval calyx lobes, corolla tube 6–7 × 1–1.5 mm, stamens of the long-styled flowers inserted near base of corolla tube, and the short-styled flowers with stamens inserted near the throat of the corolla tube and filaments not exserted the throat.