Eudonia cymatias is a moth in the Crambidae family. It was described by Meyrick in 1885. It is found in New Zealand. The wingspan is 21–22 mm. The forewings are fuscous grey, mixed with white and irrorated with black. The hindwings are pale whitish-grey, slightly tinged with ochreous. The postmedian line and a slender hindmarginal suffusion are darker grey. Adults have been recorded on wing in January.