• Thalassiosira P.T. Cleve, 1873 emend. Hasle, 1973
• Thalassiosira aculeata Proshkina-Lavrenko, 1956 (uncertain > unassessed)
• Thalassiosira adamsi Mertz, 1966 (uncertain > unassessed)
• Thalassiosira adeliae Manguin, 1957 (uncertain > unassessed)
• Thalassiosira aestivalis Gran, 1931 (uncertain > unassessed)
• Thalassiosira affinis Makarova, 1961 (uncertain > unassessed)
• Thalassiosira allenii Takano, 1965 (uncertain > unassessed)
• Thalassiosira ambigua O.G.Kozlova, 1962 (uncertain > unassessed)
• Thalassiosira andamanica A.D.Gedde, 1999 (uncertain > unassessed)
• Thalassiosira angstii (Gran) Makarova, 1971 accepted as Coscinodiscus angstii var. angstii Gran in Gran & Angst, 1931
• Thalassiosira angulata (W.Gregory) Hasle, 1978 accepted as Orthosira angulata Gregory, 1857
• Thalassiosira anguste-lineata (A.Schmidt) G.Fryxell & Hasle, 1977 accepted as Coscinodiscus angustelineatus Schmidt in Schmidt et al., 1878
• Thalassiosira annaliae Voltolina, 1971 (uncertain > unassessed)
• Thalassiosira antarctica Comber, 1896 (uncertain > unassessed)
• Thalassiosira antarctica Karsten, 1905 (uncertain > unassessed)
• Thalassiosira antarctica var. borealis G.Fryxell, Doucette & Hubbard, 1981 (uncertain > unassessed)
• Thalassiosira antiqua (Grunow) Cleve
• Thalassiosira antiqua f. inermis Sheshukova-Poretskaya, 1959 (uncertain > unassessed)
• Thalassiosira antiqua f. lapponica Sheshukova-Poretskaya, 1959 (uncertain > unassessed)
• Thalassiosira antiqua var. antiqua (Grunow) Cleve-Euler, 1941 accepted as Coscinodiscus excentricus var. antiquus Grunow, 1884
• Thalassiosira antiqua var. septata Proschkina-Lavrenko, 1955 (uncertain > unassessed)
• Thalassiosira atlantica Goryanova, 1958 (uncertain > unassessed)
• Thalassiosira aurivillii Cleve, 1901 (uncertain > unassessed)
• Thalassiosira australiensis (Grunow) Hasle in Hasle & Lange, 1989 accepted as Coscinodiscus australiensis Grunow, 1884
• Thalassiosira australis M.Peragallo, 1921 (uncertain > unassessed)
• Thalassiosira baldaufii Boden, 1993 (uncertain > unassessed)
• Thalassiosira baltica (Grunow) Ostenfeld, 1901
• Thalassiosira baltica var. baltica (Grunow in Cleve & Grunow) Ostenfeld, 1901 accepted as Coscinodiscus polyacanthus var. baltica Grunow in Cleve & Grunow, 1880
• Thalassiosira baltica var. batava Van Goor, 1920 (uncertain > unassessed)
• Thalassiosira baltica var. fluviatilis Cleve-Euler accepted as Thalassiosira subtilis var. fluviatilis Lemmermann, 1904
• Thalassiosira baltica var. genuina (Grunow in Cleve & Grunow) Cleve-Euler, 1942 accepted as Coscinodiscus polyacanthus var. baltica Grunow in Cleve & Grunow, 1880
• Thalassiosira binata Fryxell, 1977 (uncertain > unassessed)
• Thalassiosira binata var. bibinata Gao & Cheng, 1982 (uncertain > unassessed)
• Thalassiosira binata var. minor Gao & Cheng, 1992 (uncertain > unassessed)
• Thalassiosira bingensis Takano, 1980 (uncertain > unassessed)
• Thalassiosira bioculata (Grunow) Ostenfeld, 1903
• Thalassiosira bioculata var. bioculata (Grunow) Ostenfeld, 1903 accepted as Coscinodiscus bioculatus var. bioculatus Grunow, 1884 accepted as Shionodiscus bioculatus (Grunow) Alverson, Kang & Theriot, 2006
• Thalassiosira bioculata var. exigua (Grunow) Hustedt, 1928 accepted as Coscinodiscus bioculatus var. exigua Grunow, 1884
• Thalassiosira bioculata var. raripora Gaarder ex Paasche, 1961 (uncertain > unassessed)
• Thalassiosira bipartita (Rattray) Hallegraeff, 1992 accepted as Coscinodiscus bipartitus Rattray, 1890
• Thalassiosira bipora M. Shiono, 2000 (uncertain > unassessed)
• Thalassiosira blanda (A.Schmidt) T.V.Desikachary & Gowthaman, 1989 accepted as Planktoniella blanda (A.Schmidt) E.E.Syvertsen & G.R.Hasle, 1993
• Thalassiosira blandus (A. Schmidt) Desikachary & Gowthaman in Desikachary, 1989 accepted as Coscinodiscus blandus A.Schmidt, 1878
• Thalassiosira borealis Koizumi, 1980 (uncertain > unassessed)
• Thalassiosira bramaputrae (Ehrenberg) Håkansson & Locker, 1981 accepted as Stephanodiscus bramaputrae Ehrenberg, 1854
• Thalassiosira bramaputrae var. proximus (Makarova) Makarova, 1988 accepted as Coscinodiscus proximus Makarova, 1961
• Thalassiosira bramaputrae var. septentrionalis (Grunow) Makarova, 1988 accepted as Coscinodiscus septentrionalis Grunow, 1884
• Thalassiosira brunii Akiba & Yangisawa, 1985 (uncertain > unassessed)
• Thalassiosira bukryi Barron, 1983 (uncertain > unassessed)
• Thalassiosira bulbosa Syvertsen in Syvertsen & Hasle, 1984 (uncertain > unassessed)
• Thalassiosira bungerensis R.M. Gogorev & Z.V. Pushina in Gogorev et al., 2010 (uncertain > unassessed)
• Thalassiosira burckliana Schrader, 1974 (uncertain > unassessed)
• Thalassiosira californica Tanimura, 1996 (uncertain > unassessed)
• Thalassiosira cardiophora Round, 1988 (uncertain > unassessed)
• Thalassiosira caspica Makarova, 1959 (uncertain > unassessed)
• Thalassiosira castanea Akiba & Yanagisawa, 1998 (uncertain > unassessed)
• Thalassiosira catharinensis M. Garcia in M. Garcia & D. Bärwaldt Dutra, 2016
• Thalassiosira cedarkeyensis A.K.S.K.Prasad, 1993 (uncertain > unassessed)
• Thalassiosira centra M. Shiono, 2000 (uncertain > unassessed)
• Thalassiosira chilensis Krasske, 1941 (uncertain > unassessed)
• Thalassiosira clevei Gran, 1897 (uncertain > unassessed)
• Thalassiosira complicata Gersonde, 1991 (uncertain > unassessed)
• Thalassiosira concava Semina, 1991 (uncertain > unassessed)
• Thalassiosira concaviuscula I.V.Makarova, 1978 (uncertain > unassessed)
• Thalassiosira condensata Cleve, 1900 (uncertain > unassessed)
• Thalassiosira conferta Hasle, 1977 (uncertain > unassessed)
• Thalassiosira confusa Makarova, 1975 (uncertain > unassessed)
• Thalassiosira congoi Leuduger-Fortmorel, 1898 (uncertain > unassessed)
• Thalassiosira constricta Gaarder, 1938 accepted as Bacterosira constricta (Gaarder, 1938) J.S. Park & J.H. Lee, 2016
• Thalassiosira convexa V.V.Muchina, 1965 (uncertain > unassessed)
• Thalassiosira convexa var. aspinosa Schrader, 1974 (uncertain > unassessed)
• Thalassiosira coramandeliana Subrahmanyan, 1946 (uncertain > unassessed)
• Thalassiosira coromandeliana Subrahmanyan, 1946 (uncertain > unassessed)
• Thalassiosira coronata Gaarder, 1951 (uncertain > unassessed)
• Thalassiosira coronata Proschkina-Lavrenko, 1955 (uncertain > unassessed)
• Thalassiosira coronifera Proschkina-Lavrenko, 1961 (uncertain > unassessed)
• Thalassiosira cretacea Deflandre, 1941 (uncertain > unassessed)
• Thalassiosira cryophila Kisselev, 1931 (uncertain > unassessed)
• Thalassiosira cuitzeonensis I.Israde, K.Serieyssol & F.Gasse, 1998 † (uncertain > unassessed)
• Thalassiosira curiosa Hajós, 1973 (uncertain > unassessed)
• Thalassiosira curviseriata Takano, 1981 (uncertain > unassessed)
• Thalassiosira decipiens (Grunow) E.G.Jørgensen, 1905
• Thalassiosira decipiens f. levanderi (Van Goor) Takano, 1956 accepted as Thalassiosira levanderi van Goor, 1924
• Thalassiosira decipiens var. condensata (Cleve) (uncertain > unassessed)
• Thalassiosira decipiens var. decipiens (Grunow) E. Jørgensen, 1905 accepted as Coscinodiscus eccentricus var. decipiens Grunow, 1878 †
• Thalassiosira decorata Cleve-Euler, 1941 (uncertain > unassessed)
• Thalassiosira decrescens Skabichevskaya, 1984 (uncertain > unassessed)
• Thalassiosira delicata (Barron) Akiba, 1985 accepted as Thalassiosira nidulus var. delicata Barron, 1980
• Thalassiosira delicatissima Proschkina-Lavrenko, 1960 (uncertain > unassessed)
• Thalassiosira delicatissima f. aculeata Kozyrenko, 1960 (uncertain > unassessed)
• Thalassiosira delicatissima f. impalpabilis Kozyrenko, 1960 (uncertain > unassessed)
• Thalassiosira delicatissima var. delicatissima Kozyrenko, 1959 (uncertain > unassessed)
• Thalassiosira delicatula Hustedt, 1958 (uncertain > unassessed)
• Thalassiosira delicatula Ostenfeld, 1908 (uncertain > unassessed)
• Thalassiosira densannula Hasle & Fryxell, 1977 (uncertain > unassessed)
• Thalassiosira depressa M. Shiono, 2000 † (uncertain > unassessed)
• Thalassiosira dichotomica (O.G.Kozlova) G.A.Fryxell & G.R.Hasle, 1983 accepted as Porosira dichotomica O.G.Kozlova, 1962
• Thalassiosira diporocyclus Hasle, 1972 (uncertain > unassessed)
• Thalassiosira dispar (M.Peragallo & J.Héribaud) K.Serieyssol, 1998 † accepted as Coscinodiscus dispar var. dispar M. Peragallo & Héribaud in Héribaud, 1893
• Thalassiosira distans Pouchet, 1891 (uncertain > unassessed)