Chthonic (from Greek χθόνιος-khthonios, of the earth, from khthōn, earth; pertaining to the Earth; earthy) designates, or pertains to, gods or spirits of the underworld, especially in relation to Greek religion.
Greek khthon is one of several words for "earth"; it typically refers to the interior of the soil, rather than the living surface of the land (as gaia or ge does) or the land as territory (as khora does). It evokes at once abundance and the grave.
Its pronunciation is somewhat awkward for English speakers—for this reason, many American dictionaries recommend that the initial "ch" should be silent. However, most other dictionaries, such as the OED, though the Classical Greek pronunciation would have been something like .