The Swedish species of Ophion Fabricius, 1798 are revised. More than 4800 specimens and relevant type material were studied; 234 sampled specimens produced COI sequences. The study recognises 41 species, 18 of which are described as new to science, mainly from Fennoscandian material: Ophion angularis Johansson & Cederberg sp. nov., Ophion arenarius Johansson sp. nov., Ophion autumnalis Johansson sp. nov., Ophion borealis Johansson sp. nov., Ophion broadi Johansson sp. nov., Ophion brocki Johansson sp. nov., Ophion confusus Johansson sp. nov., Ophion ellenae Johansson sp. nov., Ophion inclinans Johansson sp. nov., Ophion kallanderi Johansson sp. nov., Ophion matti Johansson sp. nov., Ophion norei Johansson sp. nov., Ophion paraparvulus Johansson sp. nov., Ophion paukkuneni Johansson sp. nov., Ophion splendens Johansson sp. nov., Ophion sylvestris Johansson sp. nov., Ophion tenuicornis Johansson sp. nov. and Ophion vardali Johansson sp. nov. Barcoding analysis also indicated the possible presence of at least three additional, partly cryptic species, but these cannot be separated morphologically with certainty at this point. Ophion costatus Ratzeburg, 1848 and Ophion artemisiae Boie, 1855 are interpreted and defined. Ophion slaviceki Kriechbaumer, 1892 is excluded from synonymy with Ophion luteus Linnaeus, 1758 stat. rev. Ophion polyguttator (Thunberg, 1824) stat. rev. and Ophion variegatus Rudow, 1883 stat. rev. are excluded from synonymy with O. obscuratus Fabricius, 1798. Ophion variegatus is redescribed and a neotype is designated. Ophion albistylus Szépligeti, 1905 (syn. nov.) is synonymized with Ophion pteridis Kriechbaumer, 1879 and Ophion frontalis Strobl, 1904 (syn. nov.) is synonymized with Ophion areolaris Brauns, 1889 syn. nov. Eleven species are reported from Sweden for the first time: Ophion artemisiae, Ophion crassicornis Brock, 1982, Ophion costatus, Ophion dispar Brauns, 1895, Ophion forticornis Morley, 1915, Ophion kevoensis Jussila, 1965, Ophion ocellaris Ulbricht, 1926, Ophion perkinsi Brock, 1982, Ophion subarcticus Hellén, 1926, Ophion variegatus Rudow, 1883 and Ophion wuestneii Kriechbaumer, 1892. The study shows that a number of species that previously have been treated as highly variable taxa, actually consist of several valid species that are separable using morphological characters. An illustrated key for the determination of the Swedish Ophion species is provided.