Undines are mythical water spirits found in various folklore, particularly in European traditions. They are often depicted as beautiful female beings associated with water bodies like rivers, lakes, and oceans. In some stories, undines are said to have the ability to transform into human form, but they are also bound to the water element, which is central to their existence. The concept of undines is closely related to the broader category of elemental spirits, which represent the four classical elements: earth, air, fire, and water. The term "undine" was popularized by the 19th-century writer Paracelsus, who described them as beings that embody the essence of water.