| Gloeotromera pululahuana (Pat.) Ervin, 1956 |
| Gomphonemopsis Medlin, 1986 |
| Gomphonemopsis exigua (Kütz.) Medlin, 1986 |
| Gomphonemopsis obscura (Krasske) Lange-Bert. |
| Gomphonemopsis pseudexigua (Simonsen) Medlin, 1986 |
| Gomphoseptatum Medlin, 1986 |
| Gomphoseptatum aestuarii (Cleve) L.K. Medlin |
| Gomphosphenia Lange-Bert., 1995 |
| Gomphosphenia grovei (M. Schmidt) Lange-Bert., 1995 |
| Gossleriella F. Schütt, 1892 |
| Gossleriella tropica F. Schütt, 1892 |
| Grallomyces F. Stevens, 1918 |
| Grallomyces portoricensis F. Stevens, 1918 |
| Guepinia Fr., 1825 |
| Guepinia helvelloides (DC.) Fr., 1828 |
| Guepinia spathularia (Schwein.) Fr., 1828 |
| Gyrocephalus Pers., 1824 |
| Gyrocephalus helvelloides (DC.) Keissl., 1914 |
| Gyrothrix (Corda) Corda, 1842 |
| Gyrothrix circinata (Berk. & M. A. Curtis) S. Hughes, 1958 |