We here describe a new species of flowering plant to science, Ruellia whitneyana (Acanthaceae), so far known only from Bolivia. This species occupies wet forest understories associated with steep slopes and riparian environments, where plants grow directly atop slate rocks or among rocky soils. We postulate that this new species is of hybrid origin between Ruellia brevifolia and Ruellia puri based on recurrent sympatry and simultaneous co-flowering, intermediate vegetative and floral morphological features, and evidence from genomic and palynological data.