| Critoniopsis villaregalis (Carvajal) H. Rob., 1999 |
| Cronquistia R.M. King, 1968 |
| Cronquistia pringlei (S. Watson) R.M. King, 1968 |
| Croptilon Raf., 1837 |
| Croptilon rigidifolium (E.B. Sm.) E.B. Sm., 1981 |
| Crupina (Pers.) DC., 1810 |
| Crupina vulgaris Pers. ex Cass., 1818 |
| Cryptopetalon Cass., 1817 |
| Culcitium Bonpl., 1808 |
| Culcitium canescens Bonpl., 1808 |
| Cyanthillium Blume, 1826 |
| Cyanthillium cinereum (L.) H. Rob., 1990 |
| Cyanus Mill., 1754 |
| Cyanus segetum Hill, 1762 |
| Cyclachaena Fresen. ex Schleid., 1838 |
| Cyclachaena ambrosiifolia (A. Gray) Rydb. & Britton, 1922 |
| Cyclachaena lobata Rydb., 1922 |
| Cymophora B.L. Rob., 1907 |
| Cymophora accedens (S.F. Blake) B.L. Turner & A.M. Powell, 1977 |
| Cymophora hintonii B.L. Turner & A.M. Powell, 1977 |