| Acrodictys septosporioides Matsush, 1983 |
| Acrodictys stilboidea J. Mena & Mercado, 1986 |
| Actinocladium Ehrenb., 1819 |
| Actinocladium rhodosporum Ehrenb., 1819 |
| Actinothoe Fischer, 1889 |
| Actinothoe californica (Carlgren, 1940) |
| Acumispora Matsush., 1980 |
| Acumispora biseptata Matsush., 1980 |
| Acumispora phragmospora Matsush., 1980 |
| Acumispora verruculosa Heredia, R. F. Castañeda & R. M. Arias, 2007 |
| Aecidium Pers., 1796 |
| Aecidium cordiae Henn., 1893 |
| Aecidium mexicanum Maubl., 1904 |
| Aecidium opuntiae Magnus, 1898 |
| Aecidium pereziae Arthur, 1918 |
| Aecidium praecipuum Arthur, 1920 |
| Aecidium pulverulentum Arthur, 1906 |
| Aecidium solani Mont., 1852 |
| Aecidium zephyranthis Shear, 1902 |
| Akashiwo Gert Hansen & Moestrup, 2000 |