Abarenicola Wells, 1959 (basis of record)
Abarenicola claparedei (Levinsen, 1884) accepted as Abarenicola claparedi (Levinsen, 1884) (basis of record)
Abarenicola pusilla (Quatrefages, 1866) (basis of record)
Abyssoninoe Orensanz, 1990 (additional source)
Abyssoninoe abyssorum (McIntosh, 1885) (basis of record)
Acanthicolepis McIntosh, 1900 (additional source)
Acanthicolepis asperrima (M. Sars, 1861) (additional source)
Acholoe Claparède, 1870 (additional source)
Acrocirrus Grube, 1873 (basis of record)
Acrocirrus frontifilis (Grube, 1860) (basis of record)
Adercodon Mackie, 1994 (basis of record)
Adercodon pleijeli Mackie, 1994 (basis of record)
Aedicira Hartman, 1957 represented as Aricidea (Aedicira) Hartman, 1957 (basis of record)
Aedicira mediterranea Laubier & Ramos, 1974 accepted as Aricidea (Strelzovia) mediterranea (Laubier & Ramos, 1974) (basis of record)
Aglaophamus agilis (Langerhans, 1880) (basis of record)
Aglaophamus malmgreni (Théel, 1879) (basis of record)
Aglaophamus rubella (Michaelsen, 1897) accepted as Aglaophamus agilis (Langerhans, 1880) (basis of record)
Alciopa Audouin & Milne Edwards, 1833 (additional source)
Alciopa reynaudii Audouin & H Milne Edwards, 1833 (additional source)
Alciopina Claparède & Panceri, 1867 (additional source)
Alciopina parasitica Claparède & Panceri, 1867 (additional source)
Alkmaria Horst, 1919 (basis of record)
Alkmaria romijni Horst, 1919 (additional source)
Amaeana Hartman, 1959 (additional source)
Amaeana trilobata (Sars, 1863) (additional source)
Amage Malmgren, 1866 (additional source)
Amage adspersa (Grube, 1863) (additional source)
Amage auricula Malmgren, 1866 (basis of record)
Amage scotica Clark, 1952 (basis of record)
Amblyosyllis Grube, 1857 (basis of record)
Amblyosyllis finmarchica (Malmgren, 1867) (basis of record)
Amblyosyllis formosa (Claparède, 1863) accepted as Amblyosyllis spectabilis (Johnston in Baird, 1861) (basis of record)
Amblyosyllis granosa Ehlers, 1897 (additional source)
Amblyosyllis madeirensis Langerhans, 1879 (basis of record)
Ammotrypanella McIntosh, 1878 (basis of record)
Ampharete Malmgren, 1866 (additional source)
Ampharete acutifrons (Grube, 1860) (additional source)
Ampharete baltica Eliason, 1955 (additional source)
Ampharete falcata Eliason, 1955 (basis of record)
Ampharete finmarchica (M. Sars, 1865) (basis of record)
Ampharete goesi Malmgren, 1866 (basis of record)
Ampharete lindstroemi Hessle, 1917 (basis of record)
Ampharete petersenae Jirkov, 1997 (basis of record)
Ampharete vega (Wirén, 1883) (basis of record)
Amphicteis Grube, 1850 (additional source)
Amphicteis gunneri (M. Sars, 1835) (additional source)
Amphicteis midas (Gosse, 1855) (additional source)
Amphicteis ninonae Jirkov, 1985 (basis of record)
Amphicteis sundevalli Malmgren, 1866 (basis of record)
Amphiduros Hartman, 1959 (basis of record)
Amphiduros fuscescens (Marenzeller, 1875) (additional source)
Amphiglena Claparède, 1864 (additional source)
Amphiglena mediterranea (Leydig, 1851) (basis of record)
Amphinome Bruguière, 1789 (additional source)
Amphinome rostrata (Pallas, 1766) (additional source)
Amphitrite Müller, 1771 (additional source)
Amphitrite affinis Malmgren, 1866 represented as Neoamphitrite affinis (Malmgren, 1866) (basis of record)
Amphitrite alcicornis Fauvel, 1909 (basis of record)
Amphitrite cirrata Müller, 1776 (basis of record)
Amphitrite rubra (Risso, 1826) (additional source)
Amphitrite variabilis (Risso, 1826) (additional source)
Amphitritides gracilis (Grube, 1860) (additional source)
Amphitritides kuehlmanni Arvanitidis & Koukouras, 1995 (basis of record)
Amythasides Eliason, 1955 (additional source)
Amythasides macroglossus Eliason, 1955 (basis of record)
Ancistrosyllis McIntosh, 1878 (additional source)
Ancistrosyllis cingulata (Korschelt, 1893) (basis of record)
Ancistrosyllis fioronii Fiege & Böggemann, 1999 (basis of record)
Ancistrosyllis groenlandica McIntosh, 1878 (basis of record)
Anobothrus Levinsen, 1884 (additional source)
Anobothrus gracilis (Malmgren, 1866) (additional source)
Anoplonereis Giard, 1882 accepted as Oxydromus Grube, 1855 (basis of record)
Anoplonereis herrmanni Giard, 1882 (basis of record)
Antonbruunia Hartman & Boss, 1966 (additional source)
Antonbruunia viridis Hartman & Boss, 1965 (additional source)
Aonides Claparède, 1864 (additional source)
Aonides oxycephala (Sars, 1862) (basis of record)
Aonides paucibranchiata Southern, 1914 (basis of record)
Apharyngtus Westheide, 1971 (additional source)
Apharyngtus punicus Westheide, 1971 (additional source)
Aphelochaeta Blake, 1991 (additional source)
Aphelochaeta filiformis (Keferstein, 1862) (basis of record)
Aphelochaeta marioni (Saint-Joseph, 1894) (basis of record)
Aphelochaeta mcintoshi (Southern, 1914) (basis of record)
Aphelochaeta serrata (Eliason, 1962) accepted as Kirkegaardia serrata (Eliason, 1962) (basis of record)
Aphelochaeta vivipara (Christie, 1984) accepted as Chaetozone vivipara (Christie, 1984) (basis of record)
Aphrodita perarmata Roule, 1898 (basis of record)
Aphrogenia Kinberg, 1856 (basis of record)
Aphropharynx Wilfert, 1974 (basis of record)
Aphropharynx heterochaeta Wilfert, 1974 (basis of record)
Apistobranchus Levinsen, 1884 (additional source)
Apistobranchus tenuis Orrhage, 1962 (basis of record)
Apistobranchus tullbergi (Théel, 1879) (additional source)
Apomatus Philippi, 1844 (basis of record)
Apomatus ampulliferus Philippi, 1844 (basis of record)
Apomatus similis Marion & Bobretzky, 1875 (basis of record)
Aponuphis Kucheruk, 1978 (additional source)
Aponuphis bilineata (Baird, 1870) (additional source)
Aponuphis bilineata grubii (Marenzeller, 1886) accepted as Aponuphis grubii (Marenzeller, 1886) (basis of record)
Aponuphis brementi (Fauvel, 1916) (additional source)