| 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 |
| Carex stellulata Gooden., 1794 |
| Carex stellulata var. angustata J. Carey, 1848 |
| Carex steyermarkii Standl., 1947 |
| Carex straminea Willd. ex Schkuhr, 1801 |
| Carex straminea var. australis L.H. Bailey, 1889 |
| Carex subfusca W. Boott, 1880 |
| Carex subulata J.F. Gmel., 1791 |
| Carex tehuacana Reznicek & S. González, 2021 |
| Carex tenejapensis Reznicek & S. González, 1999 |
| Carex tetrastachya Scheele, 1849 |
| Carex thurberi Dewey, 1859 |
| Carex tojquianensis Standl. & Steyerm., 1953 |
| Carex tolucensis (F.J. Herm.) Reznicek, 1993 |