| Sigesbeckia pringlei D.L. Schulz, 1988 |
| Sigesbeckia repens B.L. Rob. & Greenm., 1895 |
| Silphium L., 1753 |
| Silphium arborescens Mill., 1768 |
| Silphium trilobatum L., 1759 |
| Silybum Adans.,1763 |
| Silybum marianum (L.) Gaertn., 1791 |
| Simsia Pers., 1807 |
| Simsia adenophora (Greenm.) S.F. Blake, 1913 |
| Simsia amplexicaulis (Cav.) Pers., 1807 |
| Simsia annectens S.F. Blake, 1917 |
| Simsia annectens var. annectens S.F. Blake, 1917 |
| Simsia annectens var. grayi (Sch. Bip. ex S.F. Blake) D.M. Spooner, 1990 |
| Simsia auriculata DC., 1836 |
| Simsia benziorum (B.L. Turner) E.E. Schill. & Panero, 2010 |
| Simsia bicentenarialis Rzed. & Calderón, 2010 |
| Simsia calva (A. Gray & Engl.) A. Gray, 1850 |
| Simsia canescens (Torr. & A. Gray) A. Gray, 1849 |
| Simsia chaseae (Millsp.) S.F. Blake, 1913 |
| Simsia cordata (Kunth) Cass., 1829 |