| Melanthera nivea (L.) Small, 1903 |
| Melanthera purpurascens S.F. Blake, 1924 |
| Melarhiza Kellogg, 1873 |
| Mendezia DC., 1836 |
| Mendezia bicolor DC., 1836 |
| Menotriche Steetz, 1864 |
| Meratia Cass., 1824 |
| Merope Wedd., 1856 |
| Metastevia Grashoff, 1975 |
| Metastevia hintonii Grashoff, 1975 |
| Mexerion G.L. Nesom, 1990 |
| Mexerion mexicanum G.L. Nesom, 1990 |
| Mexerion sarmentosum (Klatt) G.L. Nesom, 1990 |
| Mexianthus B.L. Rob., 1928 |
| Mexianthus mexicanus B.L. Rob., 1928 |
| Micrelium Forssk., 1775 |
| Microchaeta Nutt., 1841 |
| Microcoecia Hook. f., 1847 |
| Micropus L., 1753 |
| Micropus californicus Fisch. & C.A. Mey., 1835 |