Achyronychia is a monotypic genus of flowering plant containing the single species Achyronychia cooperi, which is known by the common names onyxflower and frost-mat. This plant is native to the Mojave and Sonoran Deserts of northern Mexico and the U.S. states of California, Nevada, Utah and Arizona. In California, it is known from San Diego, Imperial, Riverside, Los Angeles, San Bernardino and Inyo Counties. In Arizona, it occurs in Yuma, Mohave, Pima, Pinal and Maricopa Counties. It has also been reported from Washington County in Utah, and from Clark County, Nevada.