The South American gomphotheres were previously classified in three genera and three species. Two biogeographic corridors are recognized for the dispersion of gomphotheres in South America. Cuvieronius hyodon was found mainly in the highlands and west to the Andes, and Stegomastodon platensis and Haplomastodon chimborazi were found in lowlands. The aim of the present study is to review the taxonomy of South American lowland gomphotheres. A large sample of specimens was analyzed, which included crania, teeth and postcrania from several localities in Brazil, Ecuador, Colombia, Venezuela, Argentina, and Uruguay. A review of the diagnostic characters proposed in previous taxonomic studies of South American lowland gomphotheres found that they are variable in both reputed species if large samples are considered. There is no support for more than one South American lowland gomphothere species, and it shows a significant morphological variation in some characteristics. The name for this taxon, after a taxonomic review, must be Notiomastodon platensis (Ameghino, 1888) new combination. This reduces the number of gomphothere species in South America to two genera and species. The lowland gomphothere is closely related to Cuvieronius and Rhynchotherium, and not closely related to Stegomastodon from North America, and Sinomastodon from Asia.