Dicaeus or Dikaios (Ancient Greek: Δίκαιος) was a son of Poseidon. His brother was Syleus. They lived near the Mountain Pelion in Thessaly. He hosted Herakles.
Unlike Syleus, who was killed by Herakles, Dicaeus was a just man, which was suggested by the very literal meaning of his name (Δίκαιος = Just).
The Dicaea city in Thrace was named after him.