Mélusine or Melusine or Melusina is a figure of European folklore, a female spirit of fresh water in a holy well or river. She is usually depicted as a woman who is a serpent or fish from the waist down. She is also sometimes illustrated with wings, two tails, or both. Her legends are especially connected with the northern and western areas of France, Luxembourg, and the Low Countries.

The Nixie, Nixy, Nix, Näcken, Nicor, Nøkk, or Nøkken are humanoid, and often shapeshifting water spirits in Germanic mythology and folklore.