| Carex rhynchoperigynium S.D. Jones & Reznicek, 1992 |
| Carex rhynchophysa Liebm., 1850 |
| Carex rigens L.H. Bailey, 1884 |
| Carex robusta F. Nyl, 1844 |
| Carex rossii Boott, 1839 |
| Carex rzedowskii Reznicek & S. González, 1995 |
| Carex schiedeana Kunze, 1842 |
| Carex schiedeana var. perstricta (Mack.) F.J. Herm., 1974 |
| Carex schiedeana var. schiedeana Kunze, 1842 |
| Carex schiedeana var. stellata (Mack.) F.J. Herm., 1974 |
| Carex schottii Dewey, 1859 |
| Carex seatoniana L.H. Bailey, 1898 |
| Carex senta Boott, 1867 |
| Carex spilocarpa Steud., 1855 |
| Carex spissa L.H. Bailey, 1886 |
| Carex spissa var. seatoniana (L.H. Bailey) Kük., 1909 |
| Carex spissa var. spissa L.H. Bailey, 1886 |
| Carex spissa var. ultra (L.H. Bailey) Kük., 1909 |
| Carex standleyana Steyerm., 1952 |
| Carex stellata Mack., 1935 |