In Greek mythology, Lycus, or Lykos, referred to several people.

• Son of Poseidon and Celaeno
• Son of Dascylus of Mysia. He was hospitable towards the Argonauts and Heracles, who conquered the land of the Bebryces (Heraclea).
• Son of Hyrieus. He became the guardian of Labdacus and Laius.
• Brother of Nycteus in Greek mythology, Lycus was brother-in-law to Antiope whom Zeus impregnated. She fled in shame to King Epopeus of Sicyon and abandoned her children, Amphion and Zethus. They were exposed on Mount Cithaeron , but were found and brought up by a shepherd. Nycteus, unable to retrieve his wife, sent his brother Lycus to take her. He did so and gave her as a slave to his own wife, Dirce.
• One of the four sons of Pandion. Upon the death of Pandion, Lycus and his brothers (Aegeas, Nisos, and Pallas) took control of Athens from Metion, who had seized the throne from Pandion. They divided the government in four but Aegeas became king. He became the ancestor of the Lycians of Asia Minor.
• The person who raised Laius

Lycus was also the Roman name for the Dog River in Lebanon (Nahr-el-kalb in Arabic).