Dokos (Greek: Δοκός) is a small Greek island of the Argo-Saronic Gulf, adjacent to Hydra, and separated from the Peloponnese by a narrow strait called, on some maps, "the Hydra Gulf." It is part of the municipality of Ýdra (Hydra) in Islands regional unit and reported a population of 18 persons at the 2011 census. The island is populated only by some Orthodox monks and perennial sheep herders. The island is rocky, reaching a height of 308 metres.During the ancient times it was called Aperopia (Ἀπεροπία).