The present study represents a taxonomic revision of the P. bessonii species-group from Madagascar. Eighteen members of this group are recognized and described, and an illustrated identification key to this group is also presented. One name is raised to species level: P. decollata Forel, 1892 stat. nov. We also redescribe worker castes and designate lectotypes for P. bessonii Forel, 1891, P. decollata Forel, 1892, P. grallatrix Emery, 1899, P. madecassa Forel, 1892, and P. oswaldi 1891. The following 13 new species are described: Pheidole antsahabe sp. nov., Pheidole atsirakambiaty sp. nov., Pheidole clara sp. nov., Pheidole flammea sp. nov., Pheidole flavodepressa sp. nov., Pheidole mantadioflava sp. nov., Pheidole maro sp. nov., Pheidole ovalinoda sp. nov., Pheidole similis sp. nov., Pheidole tenebrovulgaris sp. nov., Pheidole uranus sp. nov., Pheidole voreios sp. nov., Pheidole zirafy sp. nov.
Keywords: Hymenoptera, endemic species, Malagasy region, Myrmicinae, taxonomy.