Lasianthus is a genus of flowering plants in the family Rubiaceae. They are tropical subshrubs, shrubs, or rarely, small trees. They inhabit the understory of primary forests. Lasianthus has about 180 species. The type species for the genus is . In 2012, a revision of Lasianthus in Malesia described 131 species. Another 30 or so species grow elsewhere in tropical Asia. Most of these are described in Flora of China or in . Fifteen species or perhaps as many as 20 species are known from tropical Africa. Two species (Lasianthus panamensis and Lasianthus lanceolatus), or possibly three, are native to the neotropics. Lasianthus strigosus, from Queensland, is the only species known from Australia. The Australian had at one time been placed in Lasianthus as Lasianthus graciliflorus.