A taxonomic revision of the genus Scleria (Cyperoideae, Cyperaceae) in Madagascar is presented. Herbarium specimens have been examined and 422 identified to species level. Our results recognise 25 species of Scleria from Madagascar, plus an additional heterotypic variety. Eight species are endemic to Madagascar, two are near endemic, eight taxa are also found on mainland Africa, and eight are widespread tropical taxa. Scleria achtenii is reported from Madagascar for the first time, and S. rosea is accepted at species level instead of being considered as a synonym of S. trialata. Distribution maps, conservation assessments, and notes on synonymy, ecology and ethnobotany are provided. Fourty-seven names are typified. Three rare endemic species: S. andringitrensis, S. madagascariensis and S. perpusilla, are assessed as threatened; and a recently described species, S. ankaratrensis, is indicated as Data Deficient. The most species-rich infrageneric taxa, sections Hypoporum, Abortivae and Foveolidia include 18 taxa in total, and showed strong differences in habitat preference.