Sedenia polydesma is a moth in the family Crambidae. It is found in Australia, where it has been recorded from New South Wales.[1]
The wingspan is about 16 mm. The forewings are grey whitish, sprinkled with ochreous-fuscous scales, which tend to form three moderate transverse fasciae. The hindwings are light fuscous, with two darker fuscous transverse fasciae and a fine line of fuscous scales along the hindmargin.[2]