| Muhlenbergia pauciflora Buckley, 1862 |
| Muhlenbergia pectinata C.O. Goodd., 1941 |
| Muhlenbergia pereilema P.M. Peterson, 2009 |
| Muhlenbergia peruviana (P. Beauv.) Steud., 1840 |
| Muhlenbergia peruviana f. peruviana (P. Beauv.) Steud., 1840 |
| Muhlenbergia peruviana f. versicolor Kuntze, 1898 |
| Muhlenbergia peruviana f. viridis Kuntze, 1898 |
| Muhlenbergia peruviana var. breviaristata Hack. ex Buchtien, 1920 |
| Muhlenbergia peruviana var. elatior Kuntze, 1898 |
| Muhlenbergia peruviana var. peruviana (P. Beauv.) Steud., 1840 |
| Muhlenbergia peruviana var. pulvinata (Nees) Nees & E. Mey. ex Kuntze, 1898 |
| Muhlenbergia peruviana var. subcaespitosa Kuntze, 1898 |
| Muhlenbergia phalaroides (Kunth) P.M. Peterson, 2009 |
| Muhlenbergia phleoides (Kunth) Columbus, 2010 |
| Muhlenbergia phragmitoides Griseb., 1874 |
| Muhlenbergia pilosa P.M. Peterson, Wipff & S.D. Jones, 1992 |
| Muhlenbergia plumbea (Trin.) Hitchc., 1913 |
| Muhlenbergia plumiseta Columbus, 2010 |
| Muhlenbergia polycaulis Scribn., 1911 |
| Muhlenbergia polypogon (DC.) Kunth, 1829 |