Sclerolinon is a monotypic genus of flowering plants in the flax family (Linaceae) containing the single species Sclerolinon digynum, which is known by the common names northwestern yellowflax and yellow hard flax. It is native to the western United States, where it has been recorded in Washington, Idaho, Oregon, and as far south as central California. It grows in seasonally wet habitats, such as mountain meadows and vernal pools.
It is an annual herb producing a hairless, erect stem up to 20 cm (7.9 inches) tall. The leaves are oval in shape, and the upper leaves have serrated edges. They are oppositely arranged about the stem and grow erect instead of spreading away from the stem. The inflorescence is a cyme of flowers surrounded by serrated, leaflike bracts. The flower has five yellow petals in a calyx of toothed sepals.
S. digynum is the only member of the Linaceae family which has both yellow flowers and serrated leaves.
