Oxalis lacks a treatment for Madagascar, and the genus has a reputation worldwide for being taxonomically difficult. As such we present only a first attempt at a synthesis here. In addition to the taxa treated here, several others have been associated with specimens from Madagascar, but probably in error. These include: O. bifida Thunb., O. caprina L., O. livida Jacq. (now all regarded as a South African endemic) and the widespread weedy O. anthelmintica A.Rich. We believe that there are some undescribed spp in Madagascar, but it is also possible that some of the material we have been unable to name can be placed in other known spp for Africa or elsewhere. More work is needed.