| Astragalus leptocarpus Torr. & A. Gray, 1838 |
| Astragalus leucopsis (Torr. & A. Gray) Torr., 1859 |
| Astragalus leucopsis var. lonchus M.E. Jones, 1923 |
| Astragalus longissimus (M.E. Jones) Barneby, 1964 |
| Astragalus lotiflorus Hook., 1831 |
| Astragalus lozani (M.E. Jones) Rose ex M.E. Jones, 1923 |
| Astragalus lyonnetii Barneby, 1964 |
| Astragalus macgregorii (Rydb.) Tidestr., 1937 |
| Astragalus madrensis M.E. Jones, 1923 |
| Astragalus magdalenae Greene, 1888 |
| Astragalus magdalenae var. magdalenae Greene, 1888 |
| Astragalus magdalenae var. niveus (Rydb.) Barneby, 1958 |
| Astragalus magdalenae var. peirsonii (Munz & McBurney) Barneby, 1958 |
| Astragalus mario-sousae A.E. Estrada, Villareal & Yen-Méndez, 2005 |
| Astragalus martinii Spellenb., T. Van Devender & P.D. Jenkins, 2014 |
| Astragalus metanus M.E. Jones, 1895 |
| Astragalus mexiae M.E. Jones, 1933 |
| Astragalus micranthus Desv., 1814 |
| Astragalus micranthus var. micranthus Desv., 1814 |
| Astragalus micranthus var. seatonii (M.E. Jones) Barneby, 1964 |