Aristotelia themerastis is a moth of the Gelechiidae family. It was described by Turner in 1919. It is found in Australia, where it has been recorded from New South Wales. The wingspan is 12-13 mm. The forewings are pale-grey irrorated with darker grey and with four fuscous discal dots, often partly obsolete, the first at one-third, the second on the fold obliquely beyond the first, the third at two-thirds and the fourth beneath and beyond the third. There is a slight blackish irroration at the apex and along the termen. The hindwings are grey-whitish.