Hieros gamos or Hierogamy (Greek ἱερὸς γάμος, ἱερογαμία "holy marriage") refers to a sexual ritual that plays out a marriage between a god and a goddess, especially when enacted in a symbolic ritual where human participants represent the deities. It is the harmonization of opposites.
The notion of hieros gamos does not presuppose actual performance in ritual, but is also used in purely symbolic or mythological context, notably in alchemy and hence in Jungian psychology.
Read more about Hieros Gamos: Hinduism, Ancient Near East, Greek Mythology, Tantric Buddhism, Alchemy and Jungian Psychology, Wicca