| Carex athrostachya Olney, 1868 |
| Carex atractodes F.J. Herm., 1950 |
| Carex aureolensis Steud., 1855 |
| Carex austromexicana Reznicek, 1982 |
| Carex autumnalis Mack., 1931 |
| Carex aztecica Mack., 1935 |
| Carex bajacalifornica Zika, 2019 |
| Carex ballsii Nelmes, 1940 |
| Carex barbarae Parish, 1905 |
| Carex bartlettii O'Neill, 1940 |
| Carex bella L.H. Bailey, 1892 |
| Carex bolanderi Olney, 1868 |
| Carex boliviensis van Heurck & Müll. Arg., 1870 |
| Carex boliviensis subsp. boliviensis van Heurck & Müll. Arg., 1870 |
| Carex boliviensis subsp. occidentalis Reznicek & S. González, 2001 |
| Carex bonplandii Kunth, 1837 |
| Carex brachycalama Griseb., 1879 |
| Carex brevior (Dewey) Mack., 1915 |
| Carex bromoides Willd., 1805 |
| Carex brunnipes Reznicek, 1986 |