| Merisachne Steud., 1854 |
| Merisachne drummondii Steud., 1854 |
| Merostachys Spreng., 1824 |
| Merostachys mexicana Ruiz-Sanchez & L.G. Clark, 2018 |
| Merostachys racemiflora (Steud.) E. Fourn., 1886 |
| Mesosetum Steud., 1855 |
| Mesosetum angustifolium (Swallen) Swallen, 1933 |
| Mesosetum blakei Swallen, 1937 |
| Mesosetum filifolium F.T. Hubb., 1913 |
| Mesosetum pittieri Hitchc., 1927 |
| Mesosetum stoloniferum Swallen, 1950 |
| Mesosetum tabascoënse Beetle, 1977 |
| Metcalfia Conert, 1960 |
| Metcalfia mexicana (Scribn.) Conert, 1960 |
| Michelaria Dumort., 1823 |
| Micrairoideae Pilg., 1956 |
| Microchloa R. Br., 1810 |
| Microchloa indica (L. f.) P. Beauv., 1812 |
| Microchloa kunthii Desv., 1831 |
| Micropogon Pfeiff., 1847 |