The Butterfly Effect is a 2004 American psychological thriller film directed and written by Eric Bress and J. Mackye Gruber. The film stars Ashton Kutcher, Amy Smart, Eric Stoltz and others, and was distributed by New Line Cinema. The title is a reference to the butterfly effect, which theorizes that a change in something seemingly innocuous, such as a flap of a butterfly's wings, may have unexpected larger consequences in the future, such as the path a hurricane will travel.

The film was followed by two largely unrelated direct-to-DVD sequels, The Butterfly Effect 2 and The Butterfly Effect 3: Revelations.