| Leucaena shannonii Donn. Sm., 1914 |
| Leucaena sonorensis Britton & Rose, 1928 |
| Leucaena trichandra (Zucc.) Urb., 1900 |
| Leucaena x mixtec C.E. Hughes & S.A. Harris, 1998 |
| Leucaena x spontanea C.E. Hughes & S.A. Harris, 1998 |
| Leycephyllum Piper, 1924 |
| Leycephyllum micranthum Piper, 1924 |
| Libidibia (DC.) Schltdl., 1830 |
| Libidibia coriaria (Jacq.) Schltdl., 1830 |
| Libidibia sclerocarpa (Standl.) Britton & Rose, 1930 |
| Liebrechtsia De Wild., 1902 |
| Lipusa Alef., 1866 |
| Lipusa formosa (Kunth) Alef., 1866 |
| Lipusa multiflora Alef., 1866 |
| Lojaconoa Bobrov, 1967 |
| Lojaconoa microcephala (Pursh) Bobrov, 1967 |
| Lonchocarpus Kunth, 1824 |
| Lonchocarpus acuminatus (Schltdl.) M. Sousa, 1987 |
| Lonchocarpus affinis Pittier, 1903 |
| Lonchocarpus agyrotrichus Harms, 1824 |