Kastos (Greek: Καστός) is a Greek island and a former community east of the island of Lefkada, Ionian Islands, Greece. Since the 2011 local government reform it is part of the municipality Lefkada, of which it is a municipal unit.Until 1974, when it became part of the Lefkada Prefecture, the island was administered under the Cephalonia Prefecture (Ithaca province).[3] The nearest island is Kalamos, with a deep channel between them; the mainland is approximately 5 kilometres (3 miles) to the northeast in Aetolia-Acarnania.