In Greek mythology, the name Chthonius or Chthonios (Greek: Χθόνιος "of the earth or underworld") may refer to:
Chthonius, one of the five surviving Spartoi in Thebes, father of Lycus and Nycteus (but see Hyrieus).
Chthonius, one of the sons of Aegyptus and Caliadne, who married and was killed by Bryce, daughter of Danaus and Polyxo.
Chthonius, son of Poseidon and Syme, who founded the first colony on the island of Syme, which was named after his mother.
Chthonius, a Centaur who was killed by Nestor at the wedding of Pirithous and Hippodamia.
Chthonius, one of the Gigantes.
Chthonius, an epithet of several major gods, including Zeus, Hades, Hermes, and Dionysus. See Chthonia for goddesses bearing the feminine version of the epithet.
Chthonius is also a genus of pseudoscorpions:
Chthonius (pseudoscorpion)
