| Carex pubigluma Reznicek, 1990 |
| Carex queretarensis Reznicek & S. González, 1997 |
| Carex quichensis F.J. Herm., 1950 |
| Carex revoluta Reznicek & S. González, 2021 |
| Carex rhynchoperigynium S.D. Jones & Reznicek, 1992 |
| Carex rhynchophysa Liebm., 1850 |
| Carex ringens L.H. Bailey, 1884 |
| Carex rossii Boott, 1839 |
| Carex rostrata Stokes, 1790 |
| Carex rupicola (Pedersen) G.A. Wheeler, 1996 |
| Carex rzedowskii Reznicek & S. González, 1995 |
| Carex scabrella Wahlenb., 1803 |
| Carex schaffneri Boeckeler, 1878 |
| 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 |