| Gastridium phleoides (Nees & Meyen) C.E. Hubb., 1954 |
| Gastridium scabrum C. Presl, 1826 |
| Gastridium ventricosum (Gouan) Schinz & Thell., 1913 |
| Gastropyrum (Jaub.) Á. Löve, 1982 |
| Geminata Hitchc.& Chase ex Honda, 1930 |
| Genea (Dumort.) Dumort., 1868 |
| Genea Dumort., 1823 |
| Genea madritensis (L.) Dumort., 1868 |
| Genea maxima (Desf.) Dumort., 1868 |
| Genea rigida (Roth) Dumort., 1868 |
| Genea sterilis (L.) Dumort., 1868 |
| Genea tetorum (L.) Dumort., 1868 |
| Geopogon Steud., 1840 |
| Germainiinae Clayton, 1972 |
| Gigachilon Seidl, 1836 |
| Gigantochloa Kurz ex Munro, 1868 |
| Gigantochloa aspera (Schult. & Schult. f.) Kurz, 1876 |
| Gigantochloa levis (Blanco) Merr., 1916 |
| Gimnatereas É. Desv., 1854 |
| Ginannia Bubani, 1901 |