Acacia didyma is a shrub or small tree which is native to Western Australia. It grows to between 1.5 metres and 4 metres in height and flowers from August to October (late winter to mid spring) in its native range. It occurs on East Wallabi Island in the Houtman Abrolhos as well as scattered locations near Shark Bay including Dirk Hartog Island and Carrarang and Tamala Stations The species was formally described in 1992 in the journal Nuytsia by Alex Chapman and Bruce Maslin, based on plant material collected at Shark Bay.