| Senecio metepecus B.L. Turner, 1989 |
| Senecio mexicanus McVaugh, 1972 |
| Senecio mezquitalanus B.L. Turner, 1991 |
| Senecio michoacanus (B.L. Rob.) B.L. Turner & T.M. Barkley, 1989 |
| Senecio microdontus (A. Gray) A. Heller, 1897 |
| Senecio millelobatus Rydb., 1900 |
| Senecio mohavensis A. Gray, 1884 |
| Senecio mohinorensis Greenm., 1907 |
| Senecio monoensis Greene, 1906 |
| Senecio montereyanus S. Watson, 1890 |
| Senecio moranii T.M. Barkley, 1978 |
| Senecio morelensis Miranda, 1941 |
| Senecio moreliae Hemsl., 1881 |
| Senecio mulgediifolius Schauer, 1847 |
| Senecio multicapitatus Greenm., 1906 |
| Senecio multidentatus Sch. Bip. ex Hemsl., 1881 |
| Senecio multidentatus var. huachucanus (A. Gray) T.M. Barkley, 1989 |
| Senecio multidentatus var. multidentatus Sch. Bip. ex Hemsl., 1881 |
| Senecio napeaefolius (DC.) Sch. Bip., 1845 |
| Senecio neogibsonii B.L. Turner, 1985 |