Who wrote the fairy tale that inspired Disney's The Little Mermaid?

Hans Christian Andersen wrote the fairy tale that inspired Disney's The Little Mermaid.

Andersen's Danish story, published in 1837, follows a mermaid who longs to become human and gains an immortal soul. Disney's 1989 animated film keeps the central ideas of a curious mermaid, a human prince, and a life-changing bargain, but changes the tone and ending substantially.

The original tale does not feature Ariel, Prince Eric, King Triton, Sebastian, or Ursula. Those characters were created or substantially developed for Disney's adaptation. Andersen's mermaid also does not become human simply through a royal parent's intervention; she makes a painful bargain with a sea witch.

The fairy tale belongs to Andersen's literary fairy-tale tradition rather than to the older folklore collections associated with the Brothers Grimm. Disney's film transformed the melancholy source material into a musical romance with a happy ending.