| Trifolium longifoliolum (Hemsl.) House, 1906 |
| Trifolium longifolium House, 1906 |
| Trifolium lozani House, 1906 |
| Trifolium macraei Hook. & Arn., 1833 |
| Trifolium macraei var. albopurpureum (Torr. & A. Gray) Greene, 1891 |
| Trifolium macrorrhizum Ulbr., 1906 |
| Trifolium mathewsii A. Gray, 1854 |
| Trifolium melananthum Hook. & Arn., 1838 |
| Trifolium melilotus L., 1753 |
| Trifolium melilotus var. officinalis L., 1753 |
| Trifolium mexicanum Hemsl., 1879 |
| Trifolium microcephalum Pursh, 1814 |
| Trifolium microcephalum f. velutinum McDermott, 1910 |
| Trifolium microcephalum var. lemmonii Lojac., 1883 |
| Trifolium monanthum A. Gray, 1865 |
| Trifolium morleyanum Greene, 1895 |
| Trifolium mucronatum Willd. ex Spreng., 1826 |
| Trifolium mucronatum subsp. lacerum (Greene) J.M. Gillett, 1980 |
| Trifolium mucronatum subsp. mucronatum Willd. ex Spreng., 1826 |
| Trifolium mucronatum subsp. vaughanae J.M. Gillett, 1980 |