| Muhlenbergia aguascalientensis Y. Herrera & De la Cerda, 1995 |
| Muhlenbergia alamosae Vasey, 1891 |
| Muhlenbergia alopecuroides (Griseb.) P.M. Peterson & Columbus, 2008 |
| Muhlenbergia alpestris (Kunth) Trin., 1824 |
| Muhlenbergia alta Hitchc., 1935 |
| Muhlenbergia angustifolia Swallen, 1935 |
| Muhlenbergia annua (Vasey) Swallen, 1947 |
| Muhlenbergia anomala E. Fourn., 1886 |
| Muhlenbergia appressa C.O. Goodd., 1941 |
| Muhlenbergia arachnoidea Trin. ex Kunth, 1833 |
| Muhlenbergia arenacea (Buckley) Hitchc., 1928 |
| Muhlenbergia arenicola Buckley, 1862 |
| Muhlenbergia argentea Vasey, 1886 |
| Muhlenbergia aristulata Rydb., 1905 |
| Muhlenbergia arizonica Scribn., 1888 |
| Muhlenbergia arsenei Hitchc., 1928 |
| Muhlenbergia articulata Scribn., 1891 |
| Muhlenbergia aspera Trin. ex Kunth, 1833 |
| Muhlenbergia aspericaulis Nees ex Trin., 1840 |
| Muhlenbergia asperifolia (Nees & Meyen ex Trin.) Matthei, 1984 |