"Elachista" demogenes is a moth in the Elachistidae family. It was described by Meyrick in 1897. It is found in Australia, where it has been recorded from South Australia. The wingspan is 7-8 mm. The forewings are pale grey, irrorated with dark fuscous, sometimes with a suffusiob of black irroration towards the dorsum anteriorly and toward the costa posteriorly. The plical and second discal stigmata are black. The hindwings are grey.