The Fomorians (Old Irish: Fomóire, Modern Irish: Fomhóraigh or Fomhóire) are a supernatural race in Irish mythology. They are often portrayed as hostile and monstrous beings who come from under the sea or the earth. Later, they were portrayed as giants and sea raiders. They are enemies of Ireland's first settlers and opponents of the Tuatha Dé Danann.
source: Wikipedia