Phacelia damnationensis Kierstead et al. (Hydrophyllaceae) is described as a new species from northern California. The new taxon is a large, perennial, multi-stemmed, generally upright, leafy plant growing from a branched woody caudex. Morphologically it appears most closely related to Phacelia Juss. sect. Baretiana Walden & R.Patt., which contains three other species: P. bolanderi A.Gray, P. hydrophylloides Torr. ex A.Gray, and P. procera A.Gray. This new species is currently known from five general areas in the eastern Klamath Ranges of Shasta County, where it occurs on disturbed open, rocky slopes in conifer forest habitat. We describe the morphological and habitat characteristics for P. damnationensis, another in a series of recently discovered vascular plant taxa endemic to the eastern Klamath Ranges and include an updated species key to Phacelia sect. Baretiana.