Eudonia xysmatias is a moth in the Crambidae family. It was described by Meyrick in 1907. It is found in New Zealand. The wingspan is about 19 mm. The forewings are dark fuscous with yellowish-ferruginous scales and suffused with black. The first and second lines are represented by a straight series of whitish scales surrounded with yellowish-ferruginous suffusion. The hindwings are dark grey, sprinkled with blackish.