| Ruellia montezumae Lindau, 1913 |
| Ruellia novogaliciana T.F. Daniel, 1990 |
| Ruellia nudiflora (Engelm. & A. Gray) Urb., 1912 |
| Ruellia oaxacana Leonard, 1938 |
| Ruellia obtusata S.F. Blake, 1917 |
| Ruellia occidentalis (A. Gray) Tharp & F.A. Barkley, 1949 |
| Ruellia palmeri Greenm., 1912 |
| Ruellia paniculata L., 1753 |
| Ruellia parryi A. Gray, 1878 |
| Ruellia parva (Nees) Hemsl., 1882 |
| Ruellia pedunculata Torr. ex A. Gray, 1878 |
| Ruellia peninsularis (Rose) I.M. Johnst., 1924 |
| Ruellia pereducta Standl. ex Lundell, 1934 |
| Ruellia petiolaris (Nees) T.F. Daniel, 1990 |
| Ruellia pilosa (Nees) Pav. ex Nees, 1882 |
| Ruellia pittieri Lindau, 1897 |
| Ruellia pratensis D.N. Gibson, 1972 |
| Ruellia pringlei Fernald, 1907 |
| Ruellia puberula (Leonard) Tharp & F.A. Barkley, 1949 |
| Ruellia pulcherrima T. Anderson ex Hemsl., 1882 |