The Fomorians are a supernatural race in Irish mythology. They are often portrayed as hostile and monstrous beings who come from the sea or underground.
Later, they were portrayed as giants and sea raiders. They are enemies of Ireland's first settlers and opponents of the Tuatha Dé Danann, the other supernatural race in Irish mythology. However, their relationship with the Tuath Dé is complex and some of their members intermarry and have children.
The Fomorians have thus been likened to the jötnar of Norse mythology.
The Fomorians seem to have been gods who represent the harmful or destructive powers of nature, personifications of chaos, darkness, death, blight and drought. The Tuath Dé, in contrast, seem to represent the gods of growth and civilization. It has also been suggested that the Fomorians derive from an older group of gods who were displaced by a newer group.