Sedum valens (Crassulaceae) is described from the Salmon River Canyon of central Idaho. Though it shares numerous morphological traits with Sedum borschii and S. leibergii, the species differs strikingly in having myriad leaves packed into rosettes as wide as 1 dm. The leaves are ciliate, a characteristic otherwise unknown in temperate North American Sedum, except in Sedum radiatum, a highly dissimilar species. Further distinguishing characteristics are found in leaf shape, phenology, fruit characteristics and in habitat.