The Butterfly Effect is a 2004 American science fiction thriller film written and directed by Eric Bress and J. Mackye Gruber, starring Ashton Kutcher and Amy Smart. The title refers to the butterfly effect, a popular hypothetical situation that illustrates how small initial differences may lead to large unforeseen consequences over time.
Kutcher plays 20-year-old college student Evan Treborn, with Amy Smart as his childhood sweetheart, Kayleigh Miller, William Lee Scott as her sadistic brother, Tommy, and Elden Henson as their neighbor, Lenny. Evan experiences blackouts and memory loss throughout his childhood. Later, in his 20s, Evan finds he can travel back in time to inhabit his former self during those periods of blackout, with his adult mind inhabiting his younger body. He attempts to change the present by changing his past behaviors and set things right for himself and his friends, but there are unintended consequences for all. The film draws heavily on flashbacks of the characters' lives at ages 7 and 13 and presents several alternative present-day outcomes as Evan attempts to change the past, before settling on a final outcome.
The film had a poor critical reception. It was a commercial success, producing fairly large earnings of $96 million from a budget of $13 million. The film won the Pegasus Audience Award at the Brussels International Fantastic Film Festival, and was nominated for Best Science Fiction Film at the Saturn Awards and Choice Movie: Thriller in the Teen Choice Awards, but lost to Eternal Sunshine of the Spotless Mind and The Texas Chainsaw Massacre, another film from New Line Cinema, respectively.