Endius (Endios) was a Spartan ephor during the Peloponnesian War (431–404 BC). Endius was a son of Alcibiades, member of a family whose connection with that of the Athenian Alcibiades had in a previous generation introduced into the latter this Lacedaemonian name. Apparently he was one of the three ambassadors sent by Sparta in 420 BC to dissuade Athens from entering into an alliance with Argos. They were chosen, says Thucydides, from the belief of their being acceptable to the Athenians, and possibly in particular with a view to conciliate his guest, Alcibiades, who probably made use of this very advantage in effecting the deception by which he defeated their purpose.