Yucca declinata is a species of the genus Yucca, family Asparagaceae. It is known only from the vicinity of Bacanora, in the Mexican state of Sonora. Botanist Howard Scott Gentry first collected the species and mentioned it in print, noting the differences between this population and the closely related species Y. grandiflora H. S. Gentry and Y. arizonica McKelvey (sic, = Yucca baccata var. brevifolia L. D. Benson & R. A. Darrow). He did not, however, describe it as a new species. Later examination of his descriptions and his material led to the recognition of this as a new species.