• Abyssopathes lyra (Brook, 1889)
• Acanella arbuscula (Johnson, 1862)
• Acanthogorgia armata Verrill, 1878
• Acanthogorgia hirsuta Gray, 1857
• Acanthogorgia pico Grasshoff, 1973
• Acthelmis intestinalis (Fabricius, 1780)
• Acthelmis schaudinnii Carlgren, 1921 accepted as Haliactis arctica Carlgren, 1921
• Actinauge abyssorum (Gravier, 1918) accepted as Actinauge abyssorum Carlgren, 1934
• Actinauge abyssorum Carlgren, 1934
• Actinauge richardi (Marion, 1906)
• Actinernus michaelsarsi Carlgren, 1918
• Actinia candida Müller, 1776 accepted as Metridium senile (Linnaeus, 1761)
• Actinia cari Delle Chiaje, 1822
• Actinia elongata Delle Chiaje, 1825 (unaccepted)
• Actinia equina (Linnaeus, 1758)
• Actinia equina mediterranea Schmidt, 1971 accepted as Actinia mediterranea Schmidt, 1971
• Actinia filiformis Rapp, 1829 accepted as Cereus filiformis (Rapp, 1829)
• Actinia fragacea Tugwell, 1856
• Actinia mediterranea Schmidt, 1971
• Actinia prasina Gosse, 1860
• Actinia sali Monteiro, Sole-Cava & Thorpe, 1997
• Actinia schmidti Monteiro, Sole-Cava & Thorpe, 1997 accepted as Actinia mediterranea Schmidt, 1971
• Actinia striata Quoy & Gaimard, 1833
• Actinia striata Rizzi, 1907
• Actinoscyphia aurelia (Stephenson, 1918)
• Actinoscyphia saginata (Verrill, 1882)
• Actinostola abyssorum (Danielssen, 1890)
• Actinostola callosa (Verrill, 1882)
• Actinothoe clavata (Ilmoni, 1830) accepted as Sagartiogeton undatus (Müller, 1778) accepted as Cylista undata (Müller, 1778) accepted as Sagartia undata (Müller, 1778)
• Actinothoe sphyrodeta (Gosse, 1858)
• Adamsia carciniopados (Otto, 1823) accepted as Adamsia palliata (Fabricius, 1779)
• Adamsia palliata (Bohadsch, 1761) accepted as Adamsia palliata (Fabricius, 1779)
• Adamsia palliata (Fabricius, 1779)
• Aiptasia couchii Gosse
• Aiptasia diaphana (Rapp, 1829) accepted as Exaiptasia diaphana (Rapp, 1829)
• Aiptasia mutabilis (Gravenhorst, 1831)
• Aiptasiogeton hyalinus (Delle Chiaje, 1822)
• Aiptasiogeton pellucidus (Hollard, 1848) accepted as Aiptasiogeton hyalinus (Delle Chiaje, 1822)
• Alcyonium acaule Marion, 1878
• Alcyonium aurantium Pallas, 1766 accepted as Tethya aurantium (Pallas, 1766)
• Alcyonium bocagei (Saville Kent, 1870)
• Alcyonium boletiforme Lamarck, 1815 accepted as Polymastia boletiformis (Lamarck, 1815)
• Alcyonium coralloides (Pallas, 1766)
• Alcyonium cranium Müller, 1776 accepted as Craniella cranium (Müller, 1776)
• Alcyonium cydonium Linnaeus, 1767 accepted as Geodia cydonium (Linnaeus, 1767)
• Alcyonium digitatum Linnaeus, 1758
• Alcyonium domuncula Olivi, 1792 accepted as Suberites domuncula (Olivi, 1792)
• Alcyonium epiphytum Lamarck, 1815 accepted as Protosuberites epiphytum (Lamarck, 1815)
• Alcyonium ficus Pallas, 1766 (uncertain > taxon inquirendum)
• Alcyonium glomeratum (Hassall, 1843)
• Alcyonium hibernicum (Renouf, 1931)
• Alcyonium norvegicum (Koren & Danielssen, 1883)
• Alcyonium palmatum Pallas, 1766
• Alicia costae (Panceri, 1868) accepted as Alicia mirabilis Johnson, 1861
• Alicia mirabilis Johnson, 1861
• Allantactis parasitica Danielssen, 1890
• Alternatipathes alternata (Brook, 1889)
• Amphianthus bathybium Hertwig, 1882
• Amphianthus crassus (Gravier, 1918) accepted as Gliactis crassa Gravier, 1918
• Amphianthus dohrnii (Koch, 1878)
• Amphianthus impeditus (Gravier, 1918) accepted as Stephanauge impedita (Gravier, 1918)
• Amphianthus ingolfi Carlgren, 1942
• Amphianthus inornata (Gravier, 1918) accepted as Stephanauge inornata (Gravier, 1918)
• Amphianthus islandicus Carlgren, 1942
• Amphianthus margaritaceus (Danielssen, 1890)
• Amphianthus michaelsarsi Carlgren, 1934
• Amphianthus mopseae (Danielssen, 1890)
• Amphianthus norvegicus Carlgren, 1942
• Amphianthus verruculatus Carlgren, 1942
• Andresia partenopea (Andrès, 1883)
• Andresia parthenopea (Andrès, 1883) accepted as Andresia partenopea (Andrès, 1883)
• Andvakia mirabilis Danielssen, 1890
• Andvakia parva Carlgren, 1940
• Anemonactis mazeli (Jourdan, 1880)
• Anemonia melanaster (Verrill, 1901)
• Anemonia rustica (uncertain > nomen dubium)
• Anemonia sargassensis Hargitt, 1908
• Anemonia sulcata (Pennant, 1777)
• Anemonia viridis (Forsskål, 1775)
• Anomocora fecunda (Pourtalès, 1871)
• Anomocora prolifera (Pourtalès, 1871)
• Anthelia borealis (Koren & Danielssen, 1883) accepted as Clavularia borealis Koren & Danielssen, 1883
• Anthelia fallax Broch, 1912 (uncertain > taxon inquirendum)
• Antholoba achates (Drayton in Dana, 1846)
• Anthomastus grandiflorus Verrill, 1878
• Anthomastus purpureus (Koren & Danielssen, 1883)
• Anthopleura ballii (Cocks, 1851)
• Anthopleura biscayensis (Fischer, 1874)
• Anthopleura crassa (Andrès, 1880) accepted as Cribrinopsis crassa (Andrès, 1881)
• Anthopleura rubripunctata (Grube, 1840) accepted as Bunodactis rubripunctata (Grube, 1840)
• Anthopleura thallia (Gosse, 1854)
• Anthoptilum grandiflorum (Verrill, 1879)
• Anthoptilum murrayi Kölliker, 1880
• Anthosactis ingolfi Carlgren, 1921
• Anthosactis janmayeni Danielssen, 1890
• Anthothela grandiflora (Sars, 1856)
• Anthothoe affinis (Johnson, 1861)
• Antipathella subpinnata (Ellis & Solander, 1786)
• Antipathella wollastoni (Gray, 1857)
• Antipathes (Cirripathes) setacea Gray, 1860 accepted as Stichopathes setacea (Gray, 1860)