The Water Horse: Legend of the Deep (stylised on-screen as simply The Water Horse) is a 2007 fantasy film directed by Jay Russell and written by Robert Nelson Jacobs, based on Dick King-Smith's children's novel The Water Horse. It stars Alex Etel as a young boy who discovers a mysterious egg and cares for what hatches out of it: a "water horse" (loosely based on the Celtic water horse) which later becomes the fabled Loch Ness Monster. The film also stars Emily Watson, Ben Chaplin and David Morrissey.

The film was produced by Revolution Studios and Walden Media, in collaboration with Beacon Pictures, and was distributed by Columbia Pictures. Visual effects were completed by the New Zealand–based companies Weta Digital and Weta Workshop. The Water Horse was released in the United States on 25 December 2007 and in the United Kingdom on 8 February 2008.