| Scirpus plicarhachis Griseb., 1866 |
| Scirpus potosiensis C.B. Clarke, 1908 |
| Scirpus potosinus Britton, 1892 |
| Scirpus pringlei Britton, 1888 |
| Scirpus pungens Vahl, 1806 |
| Scirpus pungens var. longispicatus (Britton) Cronquist, 1977 |
| Scirpus pungens var. pungens Vahl, 1806 |
| Scirpus pycnostachyus Salzm. ex Steud., 1855 |
| Scirpus quadrangulatus Michx., 1803 |
| Scirpus radicans Poir., 1805 |
| Scirpus remireoides Griseb., 1874 |
| Scirpus reticulatus Lam., 1791 |
| Scirpus retroflexus Poir., 1804 |
| Scirpus riparius J. Presl & C. Presl, 1830 |
| Scirpus robustus Pursh, 1814 |
| Scirpus robustus var. campestris (Britton) Fernald, 1900 |
| Scirpus robustus var. compactus Jeps., 1901 |
| Scirpus robustus var. paludosus (A. Nelson) Fernald, 1900 |
| Scirpus rostellatus Torr., 1836 |
| Scirpus rubiginosus Beetle, 1941 |