Calothamnus formosus is a plant in the myrtle family, Myrtaceae and is endemic to the south-west of Western Australia. It is a large, spreading, densely foliaged shrub with almost cylindrical, pointed leaves and red flowers in spring or summer. There are two subspecies, differing mainly in the length of their leaves. (In 2014 Craven, Edwards and Cowley proposed that the species be renamed Melaleuca aglaia.)