• Acanthophora aokii Okamura, 1934: erect
• Acanthophora dendroides Harvey, 1855: erect
• Acanthophora muscoides (Linnaeus) Bory de Saint-Vincent, 1828: erect
• Acanthophora nayadiformis (Delile) Papenfuss, 1968: erect
• Acanthophora pacifica (Setchell) Kraft, 1979: erect
• Acanthophora ramulosa Lindenberg ex Kützing, 1843: erect
• Acanthophora spicifera (M.Vahl) Børgesen, 1910: erect
• Acetabularia acetabulum (Linnaeus) P.C. Silva, 1952: erect
• Acetabularia caliculus J.V.Lamouroux, 1824: erect
• Acetabularia chiavonica Squinabol, 1902 †: erect
• Acetabularia crenulata J.V. Lamouroux, 1816: erect
• Acetabularia crenulata J.V.Lamouroux, 1816: erect
• Acetabularia dentata Solms-Laubach, 1895: erect
• Acetabularia dentata Solms-Laubach, 1895: erect
• Acetabularia farlowii Solms-Laubach, 1895: erect
• Acetabularia farlowii Solms-Laubach, 1895: erect
• Acetabularia haemmerlingii H.G.Schweiger & Berger, 1975: erect
• Acetabularia jalakanyakae Sani, Madhu, R.K.Kohli, K.Gupta & Bast, 2021: erect
• Acetabularia kilneri J.Agardh, 1887: erect
• Acetabularia major G.Martens, 1866: erect
• Acetabularia moldavica Barattolo, Ionesi & Ţibuleac, 2019 †: erect
• Acetabularia peniculus (R.Brown ex Turner) Solms-Laubach, 1895: erect
• Acetabularia ryukyuensis Okamura & Yamada, 1932: erect
• Acetabularia schenckii K. Möbius, 1889: erect
• Acetabularia schenckii Möbius, 1889: erect
• Acrodiscus vidovichii (Meneghini) Zanardini, 1868: erect
• Acrosiphonia arcta (Dillwyn) Gain, 1912: erect
• Acrosiphonia coalita (Ruprecht) Scagel, Garbary, Golden & M.W.Hawkes, 1986: erect
• Acrosiphonia congregata (Agardh) Kjellman: erect
• Acrosiphonia duriuscula (Ruprecht) Yendo, 1916: erect
• Acrosiphonia effusa Kjellman, 1893: erect
• Acrosiphonia flabelliformis Jónsson: erect
• Acrosiphonia flaccida Kjellman: erect
• Acrosiphonia flagellata Kjellman, 1893: erect
• Acrosiphonia grandis Kjelmann, 1893: erect
• Acrosiphonia hemisphaerica Kjellman, 1893: erect
• Acrosiphonia heterocladia (Sakai) K.L.Vinogradova, 1979: erect
• Acrosiphonia incurva Kjellman, 1893: erect
• Acrosiphonia minima (Fosl.) Kjellman: erect
• Acrosiphonia orientalis (J.Agardh) P.C.Silva, 1996: erect
• Acrosiphonia penicilliformis (Foslie) Kjellman, 1893: erect
• Acrosiphonia saxatilis (Ruprecht) K.L.Vinogradova, 1979: erect
• Acrosiphonia setacea Kjellman: erect
• Acrosiphonia sonderi (Kützing) Kornmann, 1962: erect
• Acrosiphonia spinescens (Kützing) Kjellman, 1893: erect
• Acrosiphonia stolonifera Kjellman, 1893: erect
• Acrosymphyton brainardii Vroom & I.A.Abbott, 2004: erect
• Acrosymphyton caribaeum (J.Agardh) Sjöstedt, 1926: erect
• Acrosymphyton firmum M.W.Hawkes, 1982: erect
• Acrosymphyton purpuriferum (J.Agardh) G.Sjöstedt, 1926: erect
• Acrosymphyton taylorii I.A.Abbott, 1962: erect
• Acrosymphyton tenax A.J.K.Millar & Kraft, 1984: erect
• Agardhiella coulteri (Harvey) Setchell, 1897: erect
• Agardhiella floridana (Kylin) P.W.Gabrielsen ex Guimarães & Oliviera, 1996: erect
• Agardhiella mexicana E.Y.Dawson, 1944: erect
• Agardhiella ramosissima (Harvey) Kylin, 1932: erect
• Agardhiella subulata (C.Agardh) Kraft & M.J.Wynne, 1979: erect
• Aglaothamnion bipinnatum (P.Crouan & H.Crouan) Feldmann & G.Feldmann, 1948: erect
• Aglaothamnion boergesenii (Aponte & D.L.Ballantine) L'Hardy-Halos & Rueness, 1997: erect
• Aglaothamnion callophyllidicola (Yamada) Boo, I.K.Lee, Rueness & Yoshida, 1991: erect
• Aglaothamnion caudatum (J.Agardh) Feldmann-Mazoyer, 1941: erect
• Aglaothamnion chadefaudii L'Hardy-Halos, 1984: erect
• Aglaothamnion chejuense G.H.Kim & I.K.Lee: erect
• Aglaothamnion circinnatum (Womersley) Cormaci, G. Furnari & Alongi, 2023: erect
• Aglaothamnion collinsii Aponte, D.L.Ballantine & J.N.Norris, 1997: erect
• Aglaothamnion confertum (Womersley) Cormaci, G. Furnari & Alongi, 2023: erect
• Aglaothamnion cordatum (Børgesen) Feldmann-Mazoyer, 1941: erect
• Aglaothamnion decompositum (J.Agardh) Halos: erect
• Aglaothamnion diaphanum L'Hardy-Halos & Maggs, 1991: erect
• Aglaothamnion endostolon Huisman, 2018: erect
• Aglaothamnion endovagum (Setchell & N.L.Gardner) I.A.Abbott, 1972: erect
• Aglaothamnion fasciculatum (Harvey) Maggs & L'Hardy-Halos, 1993: erect
• Aglaothamnion feldmanniae Halos, 1965: erect
• Aglaothamnion felipponei (Howe) Aponte, Ballantine & J.N.Norris, 1994: erect
• Aglaothamnion flexibile N.E.Aponte & D.L.Ballantine, 1995: erect
• Aglaothamnion gaillonii (P.L.Crouan & H.M.Crouan) Halos, 1965: erect
• Aglaothamnion halliae (Collins) Aponte, D.L.Ballantine & J.N.Norris, 1997: erect
• Aglaothamnion herveyi (M.Howe) N.E.Aponte, D.L.Ballantine & J.N.Norris, 1994: erect
• Aglaothamnion monopodon Børgesen, 1945: erect
• Aglaothamnion obstipum Cowling, Kraft & J.A.West, 1998: erect
• Aglaothamnion okiense Kajimura, 1994: erect
• Aglaothamnion oosumiense Itono, 1971: erect
• Aglaothamnion priceanum Maggs, Guiry & Rueness, 1991: erect
• Aglaothamnion propebyssoides (Womersley) Cormaci, G. Furnari & Alongi, 2023: erect
• Aglaothamnion pseudobyssoides (P.Crouan & H.Crouan) Halos, 1965: erect
• Aglaothamnion rabenhorstii (Kützing) L'Hardy-Halos: erect
• Aglaothamnion sarcodiae Børgesen, 1952: erect
• Aglaothamnion scopulorum (C.Agardh) Feldmann-Mazoyer, 1941: erect
• Aglaothamnion shepherdii (Womersley) Cormaci, G. Furnari & Alongi, 2023: erect
• Aglaothamnion tenuissimum (Bonnemaison) Feldmann-Mazoyer, 1941: erect
• Aglaothamnion tripinnatum (C.Agardh) Feldmann-Mazoyer, 1941: erect
• Aglaothamnion uruguayense (W.R.Taylor) N.E.Aponte, D.L.Ballantine & J.N.Norris, 1994: erect
• Aglaothamnion violaceum (Harvey) Cormaci, G.Furnari & Alongi, 2023: erect
• Ahnfeltiopsis chnoosporoides (T.Tanaka & P.H.Hô) Masuda, 1993: erect
• Ahnfeltiopsis complicata (Kützing) P.C.Silva & DeCew, 1992: erect
• Ahnfeltiopsis densa (J.Agardh) P.C.Silva & DeCew, 1992: erect
• Ahnfeltiopsis devoniensis (Greville) P.C.Silva & DeCew, 1992: erect
• Ahnfeltiopsis fastigiata J.A.Lewis & Womersley, 1994: erect
• Ahnfeltiopsis flabelliformis (Harvey) Masuda, 1993: erect
• Ahnfeltiopsis gigartinoides (J.Agardh) P.C.Silva & DeCew, 1992: erect