Thiotricha prosoestea 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 Queensland. The wingspan is about 8 mm. The forewings are shining white with some grey suffusion along the dorsum and a bright orange apical patch occupying the apical fifth of the wing, but separated from the termen by two white spots divided by grey. A broad grey fascia precedes the apical patch and there is a black apical dot continued along the upper part of the termen. The hindwings are pale-grey with a black dot at the apex.