The taxonomy of the Tetramorium naganum, T. plesiarum, T. schaufussii, and T. severini species groups are revised for the Malagasy region. A total of 31 species are treated, of which 22 are newly described and nine redescribed. This increases the richness of the hyper-diverse genus Tetramorium in the Malagasy region to 106 species, which makes it the most species-rich genus in the region. Twenty-nine of the treated species are endemic to Madagascar, one is endemic to the Comoros, and one species is found predominantly in Madagascar but also on the island of Reunion. The T. naganum species group contains five species, which are mainly distributed in the rainforests and montane rainforests of eastern and northern Madagascar: T. alperti
sp. n., T. dalek
sp. n., T. enkidu
sp. n., T. gilgamesh
sp. n., and T. naganum Bolton, 1979. The T. plesiarum species group holds five species: T. bressleri
sp. n., T. hobbit
sp. n., T. gollum
sp. n., T. mars
sp. n., and T. plesiarum Bolton, 1979. All five are arid-adapted species occurring in the southwest and west of Madagascar. The second-most species-rich group in the region is the T. schaufussii species group with 20 species, most of which inhabit rainforests or montane rainforests of eastern and northern Madagascar. This group includes two species complexes each containing ten species: the T. cognatum complex with the species T. aspis
sp. n., T. camelliae
sp. n., T. cognatum Bolton, 1979, T. freya
sp. n., T. gladius
sp. n., T. karthala
sp. n., T. myrmidon
sp. n., T. proximum Bolton, 1979, T. rumo
sp. n., and T. tenuinode
sp. n.; and the T. schaufussii complex with the species T. merina
sp. n., T. monticola
sp. n., T. nassonowii Forel, 1892 stat. n., T. obiwan
sp. n., T. pseudogladius
sp. n., T. rala
sp. n., T. schaufussii Forel, 1891, T. sikorae Forel, 1892 (= T. latior (Santschi, 1926)), T. scutum
sp. n., T. xanthogaster Santschi, 1911. The last group treated in this study is the T. severini species group, which contains only the species T. severini (Emery, 1895). This very conspicuous species is widely distributed in the rainforests and montane rainforests of eastern and northern Madagascar. All four groups are fully revised with group diagnoses, illustrated species-level identification keys, and detailed descriptions for all species that include multifocused montage images and distribution maps.