| Rhysolepis morelensis (Greenm.) S.F. Blake, 1917 |
| Rhysolepis palmeri (A. Gray) S.F. Blake, 1917 |
| Ridan Adans., 1763 |
| Riddellia Nutt., 1841 |
| Riddellia cooperi A. Gray, 1868 |
| Riddellia tagetina Nutt., 1841 |
| Robinsonecio T.M. Barkley & J.P. Janovec, 1996 |
| Robinsonecio gerberifolius (Sch. Bip. ex Hemsl.) T.M. Barkley & Janovec, 1996 |
| Robinsonecio porphyresthes (T.M. Barkley) T.M. Barkley & Janovec, 1996 |
| Rockhausenia D.J.N. Hind, 2022 |
| Rockhausenia nubigena (Kunth) D.J.N. Hind, 2022 |
| Rojasianthe Standl. & Steyerm., 1940 |
| Rojasianthe superba Standl. & Steyerm., 1940 |
| Rojasianthinae Panero, 2002 |
| Rolandra Rottb., 1775 |
| Rolandra septans Willd. ex Less., 1829 |
| Rolandrinae Cass. ex Dumort., 1829 |
| Roldana La Llave, 1825 |
| Roldana acutangula (Bertol.) H. Rob. & Brettell, 1974 |
| Roldana albonervia (Greenm.) H. Rob. & Brettell, 1974 |