• Cycadea G. Capellini & H. Graf zu Solms-Laubach, 1892 † (uncertain)
• Cycais Thorell, 1877
• Cycas Linnaeus, 1753
• Cycasis Townes in Townes, Momoi & Townes, 1965
• Cyclas Eichwald, 1857 † accepted as Cytherina Lamarck, 1818 accepted as Cythere Müller, 1785 [Family: Ostracoda incertae sedis]
• Cyclas H. Adams & A. Adams, 1857 accepted as Lucinella Monterosato, 1884 [Family: Lucinidae]
• Cyclas Lamarck, 1798 accepted as Sphaerium Scopoli, 1777 [Family: Sphaeriidae]
• Cyclas Link, 1807 [Family: Cyrenidae]
• Cyclas Mörch, 1853 accepted as Divalinga Chavan, 1951 [Family: Lucinidae]
• Cyclas Schreber, 1789 accepted as Crudia Schreber, 1789 [Family: Fabaceae]
• Cyclos Kruger, 1823 (unaccepted)
• Cyclus Anton, 1837 (uncertain) [Family: Mollusca (awaiting allocation)]
• Cyclus Barrande, 1879 † accepted as Paterula Barrande, 1879 † [Family: Paterulidae]
• Cyclus de Koninck, 1841 † [Family: Cyclidae]
• Cyclus Jurine, 1817 (unaccepted) [Family: Sphaeriidae]
• Cyclus Leach, 1815 accepted as Cylas Latreille, 1802 [Family: Brentidae]
• Cycnus Brookes, 1828 accepted as Cygnus Bechstein, 1803 [Family: Anatidae]
• Cycnus H. Milne Edwards, 1840 accepted as Congericola van Beneden, 1854 [Family: Hatschekiidae]
• Cycnus Hübner, 1819 [Family: Lycaenidae]