Leptopus malipoensis, a new species of Phyllanthaceae from Southeast Yunnan Province, China, is described. The phylogenetic position of the new species within the genus Leptopus was analyzed based on nuclear ribosomal Internal Transcribed Spacer (nrITS) and plastid matK sequence data. The results show that L. malipoensis is highly supported to be the sister of L. fangdingianus (P. T. Li) Voronts. & Petra Hoff., a species endemic to western Guangxi Province, China. Morphologically, the new species can be distinguished from all known congeneric taxa by its long and slim branches usually pendulous or procumbent, some of its leaf laminas up to 15 cm long and 7 cm wide. It further differs from its sister species by its hirsute stems, leaves and pedicel of female flowers, longer pedicel of male flowers, 3-locular ovary and three styles. A key to all 10 accepted Leptopus species is provided.