Results from molecular phylogenetic analyses indicate that three varieties of Mentzelia multicaulis (Osterhout) J. Darlington (Loasaceae) are more closely related to other species of Mentzelia sect. Bartonia Torrey & A. Gray than to M. multicaulis var. multicaulis. We elevate three varieties of M. multicaulis, originally described from Utah, to specific rank, recognizing them as M. librina (K. H. Thorne & F. J. Smith) J. J. Schenk & L. Hufford, M. flumensevera (N. H. Holmgren & P. K. Holmgren) J. J. Schenk & L. Hufford, and M. uintahensis (N. H. Holmgren & P. K. Holmgren) J. J. Schenk & L. Hufford. Both stamen and leaf shape characters support evolutionary relationships of these species with their closest relatives among the mentzelias found in the Intermountain West of the United States.