ABSTRACT Thirteen species of the genus Galianthe have been recorded for state of Rio Grande do Sul, Brazil. The species are distributed among seven biomes, one of which contains all thirteen taxa-Subtropical Seasonal Forest. Herein a new endemic species, G. riograndensis J. Florentín & E.L. Cabral, is described, illustrated and differentiated from all other species of the genus by having 3-4 verticillate leaves and a long bifid style. In addition, the pollen grain morphology and the seed micromorphology of the new species are described and illustrated, and the conservation status assessed according to IUCN criteria. Moreover, G. chodatiana is recorded for the first time from the state, and a lectotype for G. equisetoides is designated. Most of the species of Galianthe are described and illustrated with detailed photos of living specimens. A taxonomic key for species identification, as well as comments on distribution, overall phenology and habitat, are also presented. The distribution of the new species is discussed in the context of the biogeographic region of the state, and maps and a table of species by biome are also provided.