| Eupatorium bertholdii Sch. Bip., 1856 |
| Eupatorium bertholdii var. stenophyllum Sch. Bip., 1856 |
| Eupatorium betonicifolium Mill., 1768 |
| Eupatorium bigelovii A. Gray, 1859 |
| Eupatorium billbergianum Beurl., 1856 |
| Eupatorium bimatrum Standl. & L.O. Williams, 1952 |
| Eupatorium blakei B.L. Rob., 1920 |
| Eupatorium blepharilepis Sch. Bip., 1856 |
| Eupatorium bohlmannianum (R.M. King & H. Rob.) B.L. Turner, 1997 |
| Eupatorium brandegeanum B.L. Rob., 1923 |
| Eupatorium braunii Pol., 1877 |
| Eupatorium breedlovei (R.M. King & H. Rob.) B.L. Turner, 1989 |
| Eupatorium brevipes DC., 1836 |
| Eupatorium brevipetiolatum Sch. Bip. ex Baker, 1876 |
| Eupatorium brevisetum DC., 1836 |
| Eupatorium bustamenta DC., 1836 |
| Eupatorium caeciliae B.L. Rob., 1930 |
| Eupatorium calaminthifolium Kunth, 1818 |
| Eupatorium calaminthifolium var. irrasum B.L. Rob., 1923 |
| Eupatorium calaminthifolium var. pluridentatum DC., 1836 |