| Willardia schiedeana (Schltdl.) F.J. Herm., 1947 |
| Wisteria Nutt., 1818 |
| Wisteria sinensis (Sims) Sweet, 1826 |
| Wisteria villosa Rehder, 1926 |
| Xerocassia Britton & Rose, 1930 |
| Xerocassia armata (S. Watson) Britton & Rose, 1930 |
| Xiphocarpus C. Presl, 1830 |
| Xiphocarpus martinicensis C. Presl, 1830 |
| Xylophacos Rydb., 1903 |
| Xylophacos amphioxys (A. Gray) Rydb., 1906 |
| Xylophacos aragalloides Rydb., 1907 |
| Xylophacos melanocalyx Rydb., 1925 |
| Xylophacos tephrodes (A. Gray) Rydb., 1925 |
| Xyphanthus Raf., 1817 |
| Xyphanthus hederifolius Raf., 1817 |
| Zapoteca H.M. Hern., 1987 |
| Zapoteca alinae H.M. Hern., 1989 |
| Zapoteca balsasensis H.M. Hern., 2015 |
| Zapoteca cruzii H.M. Hern., 2015 |
| Zapoteca formosa (Kunth) H.M. Hern., 1987 |