Memecylon L. (Melastomataceae, Olisbeoideae) is a widespread paleotropical genus of forest shrubs and small trees and is one of the ten most species-rich genera of woody plants in Madagascar. All of the Malagasy species are endemic to the island, and most of them are known from just one or two sites. As part of ongoing work toward a comprehensive taxonomic revision, twenty- four new Malagasy species are described and illustrated here: M. albocoronatum R.D. Stone, M. antongilense R.D. Stone, M. articulatum R.D. Stone, M. atractocarpum R.D. Stone, M. betamponense R.D. Stone, M. bullatum R.D. Stone, M. calcicola R.D. Stone, M. dipterum R. D. Stone, M. drymophilum R.D. Stone, M. florosum R.D. Stone, M. fodinae R.D. Stone, M. fusiforme R.D. Stone, M. futilifolium R.D. Stone, M. iantarense R.D. Stone, M. ingens R.D. Stone & D. Turk, M. lemuricum R.D. Stone, M. marojejense R.D. Stone, M. montisgallicorum R.D. Stone, M. naviculiforme R.D. Stone, M. pseudomocquerysii R.D. Stone, M. pseudopulvinatum R.D. Stone, M. subaridum R.D. Stone, M. subundulatum R.D. Stone, and M. triflorum R.D. Stone. The conservation status of each species is provisionally assessed in accordance with the IUCN Red List Categories and Criteria.