| Castilleja purpusii Brandegee, 1904 |
| Castilleja quiexobrensis G.L. Nesom, 1995 |
| Castilleja racemosa (Breedlove & Heckard) T.I. Chuang & Heckard, 1991 |
| Castilleja retrorsa Standl., 1909 |
| Castilleja rhizomata N.H. Holmgren, 1976 |
| Castilleja rigida Eastw., 1909 |
| Castilleja roei Crosswh., 1970 |
| Castilleja salaisolaveae J.M. Egger, Velazco & Huereca, 2022 |
| Castilleja saltensis Eastw., 1909 |
| Castilleja scabridula Eastw., 1909 |
| Castilleja schaffneri Hemsl., 1882 |
| Castilleja scorzonerifolia Kunth, 1818 |
| Castilleja sessiliflora Pursh, 1813 |
| Castilleja setosa Pennell, 1940 |
| Castilleja socorrensis Moran, 1989 |
| Castilleja speciosa M. Martens & Galeotti, 1845 |
| Castilleja sphaerostigma Eastw., 1909 |
| Castilleja spiranthoides Standl., 1936 |
| Castilleja stenantha A. Gray, 1878 |
| Castilleja stenophylla M.E. Jones, 1908 |