• Acanthophora aokii Okamura, 1934: epilithic
• Acanthophora dendroides Harvey, 1855: epilithic
• Acanthophora muscoides (Linnaeus) Bory de Saint-Vincent, 1828: epilithic
• Acanthophora nayadiformis (Delile) Papenfuss, 1968: epilithic
• Acanthophora pacifica (Setchell) Kraft, 1979: epilithic
• Acanthophora ramulosa Lindenberg ex Kützing, 1843: epilithic
• Acanthophora spicifera (M.Vahl) Børgesen, 1910: epilithic
• Acetabularia acetabulum (Linnaeus) P.C. Silva, 1952: epilithic
• Acetabularia caliculus J.V.Lamouroux, 1824: epilithic
• Acetabularia chiavonica Squinabol, 1902 †: epilithic
• Acetabularia crenulata J.V. Lamouroux, 1816: epilithic
• Acetabularia crenulata J.V.Lamouroux, 1816: epilithic
• Acetabularia dentata Solms-Laubach, 1895: epilithic
• Acetabularia dentata Solms-Laubach, 1895: epilithic
• Acetabularia farlowii Solms-Laubach, 1895: epilithic
• Acetabularia farlowii Solms-Laubach, 1895: epilithic
• Acetabularia haemmerlingii H.G.Schweiger & Berger, 1975: epilithic
• Acetabularia jalakanyakae Sani, Madhu, R.K.Kohli, K.Gupta & Bast, 2021: epilithic
• Acetabularia kilneri J.Agardh, 1887: epilithic
• Acetabularia major G.Martens, 1866: epilithic
• Acetabularia moldavica Barattolo, Ionesi & Ţibuleac, 2019 †: epilithic
• Acetabularia peniculus (R.Brown ex Turner) Solms-Laubach, 1895: epilithic
• Acetabularia ryukyuensis Okamura & Yamada, 1932: epilithic
• Acetabularia schenckii K. Möbius, 1889: epilithic
• Acetabularia schenckii Möbius, 1889: epilithic
• Acrodiscus vidovichii (Meneghini) Zanardini, 1868: epilithic
• Acrosiphonia arcta (Dillwyn) Gain, 1912: epilithic
• Acrosiphonia coalita (Ruprecht) Scagel, Garbary, Golden & M.W.Hawkes, 1986: epilithic
• Acrosiphonia congregata (Agardh) Kjellman: epilithic
• Acrosiphonia duriuscula (Ruprecht) Yendo, 1916: epilithic
• Acrosiphonia effusa Kjellman, 1893: epilithic
• Acrosiphonia flabelliformis Jónsson: epilithic
• Acrosiphonia flaccida Kjellman: epilithic
• Acrosiphonia flagellata Kjellman, 1893: epilithic
• Acrosiphonia grandis Kjelmann, 1893: epilithic
• Acrosiphonia hemisphaerica Kjellman, 1893: epilithic
• Acrosiphonia heterocladia (Sakai) K.L.Vinogradova, 1979: epilithic
• Acrosiphonia incurva Kjellman, 1893: epilithic
• Acrosiphonia minima (Fosl.) Kjellman: epilithic
• Acrosiphonia orientalis (J.Agardh) P.C.Silva, 1996: epilithic
• Acrosiphonia penicilliformis (Foslie) Kjellman, 1893: epilithic
• Acrosiphonia saxatilis (Ruprecht) K.L.Vinogradova, 1979: epilithic
• Acrosiphonia setacea Kjellman: epilithic
• Acrosiphonia sonderi (Kützing) Kornmann, 1962: epilithic
• Acrosiphonia spinescens (Kützing) Kjellman, 1893: epilithic
• Acrosiphonia stolonifera Kjellman, 1893: epilithic
• Acrosorium acrospermum (J.Agardh) Kylin, 1938: epilithic
• Acrosorium amphiroae Jaasund, 1976: epilithic
• Acrosorium ciliolatum (Harvey) Kylin, 1924: epilithic
• Acrosorium cincinnatum M.J.Wynne, 1986: epilithic
• Acrosorium decumbens (J.Agardh) Kylin, 1929: epilithic
• Acrosorium deformatum (Suhr) Papenfuss, 1943: epilithic
• Acrosorium flabellatum Yamada, 1930: epilithic
• Acrosorium fragile W.R.Taylor, 1945: epilithic
• Acrosorium krishnamurthyi M.Umamaheswara Rao, 2002: epilithic
• Acrosorium maculatum (Sonder ex Kützing) Papenfuss, 1940: epilithic
• Acrosorium minus (Sonder) Kylin, 1924: epilithic
• Acrosorium odontophorum M.A.Howe & W.R.Taylor, 1931: epilithic
• Acrosorium papenfussii W.R.Taylor, 1945: epilithic
• Acrosorium polyneurum Okamura, 1936: epilithic
• Acrosorium procumbens E.Y.Dawson, 1961: epilithic
• Acrosorium venulosum (Zanardini) Kylin, 1924: epilithic
• Acrosorium yendoi Yamada, 1930: epilithic
• Acrospongium ralfsioides Schiffner, 1916: epilithic
• Acrosymphyton brainardii Vroom & I.A.Abbott, 2004: epilithic
• Acrosymphyton caribaeum (J.Agardh) Sjöstedt, 1926: epilithic
• Acrosymphyton firmum M.W.Hawkes, 1982: epilithic
• Acrosymphyton purpuriferum (J.Agardh) G.Sjöstedt, 1926: epilithic
• Acrosymphyton taylorii I.A.Abbott, 1962: epilithic
• Acrosymphyton tenax A.J.K.Millar & Kraft, 1984: epilithic
• Acrothrix gracilis Kylin, 1907: epilithic
• Acrothrix mirabilis Kylin: epilithic
• Acrothrix novaeangliae W.R.Taylor: epilithic
• Acrothrix pacifica Okamura & Yamada, 1932: epilithic
• Aegagropila brownii (Dillwyn) Kützing, 1854: epilithic
• Aegagropila globulus K.Meier, 1927: epilithic
• Aegagropila kannoi Tokida, 1954: epilithic
• Aegagropila montagneana (Kützing) Kützing, 1854: epilithic
• Aeodes dilatata Yamada: epilithic
• Aeodes nitidissima J.Agardh, 1876: epilithic
• Agardhiella coulteri (Harvey) Setchell, 1897: epilithic
• Agardhiella floridana (Kylin) P.W.Gabrielsen ex Guimarães & Oliviera, 1996: epilithic
• Agardhiella mexicana E.Y.Dawson, 1944: epilithic
• Agardhiella ramosissima (Harvey) Kylin, 1932: epilithic
• Agardhiella subulata (C.Agardh) Kraft & M.J.Wynne, 1979: epilithic
• Aglaothamnion boergesenii (Aponte & D.L.Ballantine) L'Hardy-Halos & Rueness, 1997: epilithic
• Aglaothamnion callophyllidicola (Yamada) Boo, I.K.Lee, Rueness & Yoshida, 1991: epilithic
• Aglaothamnion caudatum (J.Agardh) Feldmann-Mazoyer, 1941: epilithic
• Aglaothamnion chadefaudii L'Hardy-Halos, 1984: epilithic
• Aglaothamnion chejuense G.H.Kim & I.K.Lee: epilithic
• Aglaothamnion circinnatum (Womersley) Cormaci, G. Furnari & Alongi, 2023: epilithic
• Aglaothamnion collinsii Aponte, D.L.Ballantine & J.N.Norris, 1997: epilithic
• Aglaothamnion confertum (Womersley) Cormaci, G. Furnari & Alongi, 2023: epilithic
• Aglaothamnion cordatum (Børgesen) Feldmann-Mazoyer, 1941: epilithic
• Aglaothamnion decompositum (J.Agardh) Halos: epilithic
• Aglaothamnion diaphanum L'Hardy-Halos & Maggs, 1991: epilithic
• Aglaothamnion endostolon Huisman, 2018: epilithic
• Aglaothamnion endovagum (Setchell & N.L.Gardner) I.A.Abbott, 1972: epilithic
• Aglaothamnion fasciculatum (Harvey) Maggs & L'Hardy-Halos, 1993: epilithic
• Aglaothamnion feldmanniae Halos, 1965: epilithic