The Nuckelavee (or Nuckalavee) is a creature from Orcadian folklore. The name is a later corruption of the Orcadian name "knoggelvi", which in turn seems to be a variant of the "Nokk" or "Nuggle", and is thus related to the Icelandic Nykur.

He resembles a centaur whose legs are part fin; he has an enormous gaping mouth and a single giant eye, which burns with a red flame. The most gruesome detail of his appearance is the fact that he has no skin. black blood courses through yellow veins, and the pale sinews and powerful muscles are visible as a pulsating mass. The Nuckelavee has an aversion to running water, and those who are chased by him have only to cross a stream to be rid of him. Some reports claim that he is simply a very large head on two small arms, with all of the other characteristics mentioned above.

The other fear of the Nukelavee is the smell of burning seaweed to create kelp. This will enrage the Nukelavee sending it into a fit of rage he would go on killing fields of cattle the only person that can stop him is The Mither O'the Sea, another ancient god-like being of Orkney mythology.