Acacia formidabilis is a shrub of the genus Acacia and the subgenus Plurinerves that is endemic to south western Australia.
The diffuse pungent shrub typically grows to a height of 0.2to with hairy branchlets that have persistent recurved spinoose stipules with a length of . Like most species of Acacia it has phyllodess rather than true leaves. The evergreen patent to ascending phyllodes have an inequilaterally narrowly elliptic to oblong-lanceolate shape and can be shallowly recurved. The pale green to grey-green, pungent, leathery, glabrous and rigid phyllodes have a length of and a width of and have many fine parallel nerves.[1] It blooms from August to September and produces yellow flowers.
It is native to an area in the Wheatbelt and Goldfields regions of Western Australia where it is commonly found in undulating plains and hillsides growing in sandy soils. The shrub has a scattered distribution from around Paynes Find and Perenjori in the north down to around Southern Cross in the south where it is usually a part of tall open shrubland communities.[1]