| Astragalus niveus (Rydb.) Barneby, 1944 |
| Astragalus nothoxys A. Gray, 1864 |
| Astragalus nuttallianus DC., 1825 |
| Astragalus nuttallianus var. austrinus (Small) Barneby, 1964 |
| Astragalus nuttallianus var. cedrosensis M.E. Jones, 1923 |
| Astragalus nuttallianus var. imperfectus (Rydb.) Barneby, 1942 |
| Astragalus nuttallianus var. zapatanus Barneby, 1956 |
| Astragalus orcuttianus S. Watson, 1885 |
| Astragalus orizabae Seaton, 1893 |
| Astragalus orizabae var. irolanus M.E. Jones, 1923 |
| Astragalus orthanthus A. Gray, 1864 |
| Astragalus oxyphysopsis Barneby, 1976 |
| Astragalus oxyphysus A. Gray, 1864 |
| Astragalus oxyrhynchus Hemsl., 1879 |
| Astragalus painteri Rose ex Jones, 1923 |
| Astragalus palmeri A. Gray, 1868 |
| Astragalus parishii A. Gray, 1883 |
| Astragalus parvus Hemsl., 1879 |
| Astragalus peirsonii Munz & McBurney, 1932 |
| Astragalus pennellianus Barneby, 1964 |