| 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 |
| Astragalus militaris M.E. Jones, 1923 |
| Astragalus miserandus Greene, 1895 |
| Astragalus mollissimus Torr., 1827 |
| Astragalus mollissimus var. bigelovii (A. Gray) Barneby, 1964 |
| Astragalus mollissimus var. earlei (Greene ex Rydb.) Tidestr., 1935 |
| Astragalus mollissimus var. irolanus (M.E. Jones) Barneby, 1964 |
| Astragalus mollissimus var. nitens Barneby, 1964 |
| Astragalus moranii Barneby, 1976 |
| Astragalus nigrescens Pall., 1800 |
| Astragalus niquiriciaefolius Sessé & Moc., 1894 |