Metathrinca memnon is a moth in the Xyloryctidae family. It was described by Meyrick in 1914. It is found in Sri Lanka. The wingspan is about 24 mm. The forewings are silvery-white with the costal edge blackish towards the base and a slender slightly curved blackish streak from the dorsum beyond the middle, reaching about half across the wing. There are several very fine linear dark-fuscous marks around the apex and termen. The hindwings are ochreous-whitish.