Eurybia saxicastelli, commonly known as the Rockcastle aster, is an herbaceous perennial native to the south eastern United States. It is present only in the states of Kentucky and Tennessee along the Rockcastle River and the nearby Big South Fork River. As a result of its extremely restricted range as well as human alterations to its habitat, it is considered critically imperiled by the Nature Conservancy. The flowers appear in the late summer through fall and have ray florets that are pale blue to pale white and yellow disc florets that turn purplish with age.