| Senecio cirsioides Hemsl., 1881 |
| Senecio claryae B.L. Turner, 1993 |
| Senecio coahuilensis Greenm., 1907 |
| Senecio cobanensis J.M. Coult., 1891 |
| Senecio confusus Britten, 1898 |
| Senecio conzattii Greenm., 1907 |
| Senecio copeyensis Greenm., 1907 |
| Senecio cordovensis Hemsl., 1881 |
| Senecio coronopus Nutt., 1841 |
| Senecio coulteri Greenm., 1914 |
| Senecio cristobalensis Greenm. ex Loes., 1906 |
| Senecio cronquistii (H. Rob. & Brettell) B.L. Turner & T.M. Barkley, 1989 |
| Senecio ctenophyllus Greenm., 1907 |
| Senecio cyclophyllus Greenm., 1907 |
| Senecio decorticans A. Nelson, 1936 |
| Senecio decorus Greenm., 1907 |
| Senecio deformis Klatt, 1888 |
| Senecio deppeanus Hemsl., 1881 |
| Senecio doratophyllus Benth., 1841 |
| Senecio douglasii DC., 1838 |