The dusky grasswren (Amytornis purnelli) is a species of small passerine bird in the family Maluridae. The species is endemic to Australia but is limited to inland areas of the Northern Territory, Western Australia and South Australia. The dusky grasswren is superficially similar in appearance to a number of the other grasswrens in the genus Amytornis, but is the only member of this genus to exclusively inhabit rocky ranges across Central Australia. It has a predominantly brown base colour to its plumage with fine pale streaking over the head breast and mantle. The brown of the plumage is a richer chestnut on the back and pale to almost buff on the belly and vent. The most obvious difference between sexes is the bright rusty-brown spot on the fore-flanks of the adult female and all birds exhibit the characteristic cocked tail posture common to all malurids.