The red imported fire ant was first described by Swiss entomologist Felix Santschi in a 1916 journal article published by "Physis". Originally named "Solenopsis saevissima wagneri" from a syntype worker collected from Santiago del Estero, Argentina, Santschi believed the ant was a variant of "S. saevissima"; the specific epithet, "wagneri", derives from the surname of E.R. Wagner, who collected the first specimens. The type material is currently housed in Naturhistorisches Museum Basel, Switzerland, but additional type workers are possibly housed in the Muséum national d'histoire naturelle, Paris. In 1930, American myrmecologist William Creighton reviewed the genus "Solenopsis" and reclassified the taxon as "Solenopsis saevissima electra wagneri" at rank, noting that he could not collect any workers that referred to Santschi's original description. In 1952, the "S. saevissima" species complex was examined and, together with nine other species-group names, "S. saevissima electra wagneri" was synonymised with "S. saevissima saevissima". This reclassification was accepted by Australian entomologist George Ettershank in his revision of the genus and in Walter Kempf's 1972 catalogue of Neotropical ants.