| Carex leptalea Wahlenb., 1803 |
| Carex leucodonta Holm, 1903 |
| Carex liebmannii Walp., 1852 |
| Carex lithosperma (L.) L., 1774 |
| Carex longicaulis Boeckeler, 1882 |
| Carex longicaulis var. coulteri (W. Boott ex Hemsl.) Kük., 1909 |
| Carex longii Mack., 1922 |
| Carex longiligula Reznicek & S. González, 2001 |
| Carex longissima M.E. Jones, 1933 |
| Carex lurida Wahlenb., 1803 |
| Carex mackenziana Weath., 1936 |
| Carex macloviana d'Urv., 1825 |
| Carex macloviana subsp. subfusca (W. Boott) T. Koyama, 1989 |
| Carex macloviana var. subfusca (W. Boott) Kük., 1909 |
| Carex macrosperma Mack., 1909 |
| Carex maculata Liebm., 1850 |
| Carex madrensis L.H. Bailey, 1898 |
| Carex marcida Boott, 1839 |
| Carex marianensis Stacey, 1937 |
| Carex mcvaughii Reznicek, 1982 |