A new species, Goniothalamusflagellistylus Tagane & V. S. Dang, sp. nov. from Hon Ba Nature Reserve in Khanh Hoa Province, South Vietnam is described and illustrated. This species is most similar to Goniothalamustortilipetalus M.R.Hend., but distinct in having 308-336 stamens (vs. ca. 170-260) and ca.120 carpels (vs. ca. 50-100) per flower, and Stigma and pseudostyles ca.8.5 mm (vs. 4-4.5 mm) long.
Keywords: Annonaceae; Goniothalamus; Hon Ba Nature Reserve; Vietnam.