The genus Typosyllis (Langerhans, 1879) (Polychaeta: Syllidae: Syllinae) is revised for the first time. All distinct species of this taxon are described in detail and synonyms listed. Altogether, more than 1850 specimens representing 213 taxa were examined. Twenty-three taxa, previously assigned to Syllis, Langerhansia, Ehlersia or Pionosyllis, are transferred to the genus Typosyllis. Eight species previously assigned to Typosyllis or Syllis are transfered to other syllid taxa. One junior homonym is renamed. The following four species are described as new to science: T. hyllebergi sp. nov., T. mauretanica sp. nov., T. silkeae sp. nov. and T. taiwanensis sp. nov. Three names are treated as Syllinae incertae sedis. Fifty-five names are regarded as younger synonyms of previously described Typosyllis-species. Fifty-seven names are considered nomina dubia. Nine names are considered nomina nuda. The names Syllis atlantico and S. atlantica lineata originally erected as nomina nova have to be eliminated. According to this revision the genus Typosyllis comprises 107 distinct species. A key for identification of all species is provided. Four lectotypes and several paralectotypes are designated: Typosyllis vittata (Grube, 1840) (MPW 673), T. valida Grube, 1857 (ZMUC 881; ZMUC 890), T. neglecta (Grube, 1870) comb. nov. (ZMB Verm. 843 (LT); ZMB Verm. 11074 (PLT)) und T. violacea (Grube, 1870) comb. nov. (ZMB Verm. 844; ZMB 11073). For two species neotypes are designated: Typosyllis cornuta (Rathke, 1843) (NTNU) und T. prolifera (Krohn, 1852) (NHMG Inve-21334). In the computer-based, cladistic analysis of Typosyllis revealed 3 large monophyletic groups of complexes: the complex-group cornuta (22 species, 6 species-groups), the complex-group prolifera (49 species, 8 species-groups) and the complex-group armillaris (25 species, 4 species-groups). Eleven species cannot be assigned with certainty to any of these 18 species-groups. It is shown that the taxa previously assigned to the genus Langerhansia (species with falcigerous and pseudospinigerous chaetae) probably form a monophylum, whereas the taxa previously assigned to the genus Typosyllis (species with falcigerous chaetae only) form a paraphylum. Nevertheless, the taxa Langerhansia is eliminated by referring the respective species to the genus Typosyllis, since the distinction of these two groups is based only on slight, gradual differences in some characters, providing no sound reasoning for a correct assignment of some species to Typosyllis or to Langerhansia.
