• Achelium Dejean, 1833 accepted as Achenium Leach in Samouelle, 1819
• Acolium (Acharius) S.F. Gray, 1821 accepted as Cyphelium Acharius, 1815
• Acolium Trevisan, 1862 accepted as Cyphelium Acharius, 1815
• Actium Casey, 1887
• Adelium Kirby, 1819
• Adenium J.J. Roemer & J.A. Schultes, 1819
• Adrium Pascoe, 1866
• Aeonium Webb & Berthelot, 1840
• Agenium C.G.D. Nees in J. Lindley, 1836
• Agrium Agassiz, 1846 accepted as Agrion Fabricius, 1775
• Aidium Popov, 1968 † (uncertain)
• Aletium Trinchese, 1881 (uncertain)
• Allium Linnaeus, 1753
• Amesium Newman, 1844 accepted as Asplenium Linnaeus, 1753
• Anbium Chûjô, 1964 accepted as Anobium Fabricius, 1775
• Anetium Splitgerber, 1840
• Angelium Opiz in Berchtold & Opiz, 1839 (uncertain)
• Apedium G.R. Chiron, A. Sambin & G.J. Braem, 2015 accepted as Selenipedium H.G. Reichenbach, 1854
• Arnium Nitschke ex G. Winter, 1873
• Ascium Schreber, 1789 (uncertain)
• Athelium Nylander, 1886 accepted as Thelocarpon Nylander, 1853