The Butterfly Effect is a 2004 American fantasy/drama movie starring Ashton Kutcher, Amy Smart, Eric Stoltz, and others, distributed by New Line Cinema. The title is a reference to the butterfly effect, which theorises that a change in something seemingly innocuous, such as a flap of a butterfly's wings, may cause unexpected larger changes in the future, such as a tornado. The Butterfly Effect is directed and written by Eric Bress and J. Mackye Gruber.

The movie was followed by a largely unrelated direct-to-DVD sequel, The Butterfly Effect 2.