Phymatocarpus interioris is a plant in the myrtle family, Myrtaceae and is endemic to the south-west of Western Australia. It resembles many small species of Melaleuca, mainly differing in the way its anthers are attached at the top of the stamens. In Phymatocarpus they are attached at their base and open at the other end through two slits. It is a shrub with many small heads of pink to purple flowers fading to white, often covering the plant for several weeks in spring. It is most closely related to Phymatocarpus porphyrocephalus and was only recognised as a new species in 1999.