Annwn ([ˈanʊn]), or Annwfn ([ˈanʊvn]), is the Otherworld in Welsh mythology. Ruled by Arawn (or, in Arthurian literature, by Gwyn ap Nudd),
Middle Welsh sources suggest that the term was recognised as meaning "very deep" in medieval times. The appearance of a form antumnos on an ancient Gaulish curse tablet, which means an ('other') + tumnos ('world'), however, suggests that the original term may have been *ande-dubnos, a common Gallo-Brittonic word that literally meant "underworld".