Craven & R.D.Edwards Calothamnus pachystachyus is a plant in the myrtle family, Myrtaceae and is endemic to the south-west of Western Australia.

It is an erect, much-branched shrub with thick bark, flat leaves and clusters of red flowers in spring.

There are 4 petals and the stamens are arranged in 4 claw-like bundles, the upper two broad and flat and the lower ones narrow and lacking anthers.

[7] Calothamnus pachystachyus occurs near the boundary between the Avon Wheatbelt, Jarrah Forest and Swan Coastal Plain biogeographic regions[5][8] where it grows soils derived from laterite on ridges and roadsides.

[9] Calothamnus pachystachyus is classified as "Priority Four" by the Western Australian government Department of Parks and Wildlife[5] meaning that is rare or near threatened.