Adelpha ethelda, the Ethelda Sister, is a butterfly of the Nymphalidae family. It was described by Hewitson in 1867. It is found from Mexico to Ecuador. The habitat consists of pre-montane rainforests and cloudforests at altitudes ranging from 400 to 2,000 meters. The wingspan is 34–37 mm. Adult males have been recorded imbibing mineralised moisture from damp soil, boulders, sandy river beaches or from aphid secretions on foliage. Larvae have been recorded feeding on Sabicea aspera.