Memento is a 2000 American psychological thriller film written and directed by Christopher Nolan, adapted from his younger brother Jonathan's short story "Memento Mori". It stars Guy Pearce as Leonard Shelby, a man with anterograde amnesia which renders his brain unable to store new memories. During the opening credits, (which portrays the end of the story) it is shown that Leonard kills Teddy (Joe Pantoliano) for the rape and murder of his wife based on information provided by Natalie (Carrie-Anne Moss).

This film is often used to show the distinction between plot and story. The film's events unfold in two separate, alternating narratives — one in color, and the other in black and white. The black and white sections are told in chronological order, showing Leonard conversing with an anonymous phone caller in a motel room. Leonard's investigation is depicted in color sequences that are in reverse chronological order. As each sequence begins, the audience is unaware of the preceding events, just like Leonard, thereby giving the viewer a sense of his confusion. By the film's end when the two narratives converge we understand the investigation and the events that lead up to Teddy's death.

Memento premiered on September 5, 2000, at the Venice Film Festival to critical acclaim and received a similar response when it was released in European theaters starting in October 2000. Critics especially praised its unique, nonlinear narrative structure and themes of memory, perception, grief, self-deception, and revenge. The film was successful at the box office and received numerous accolades, including Academy Award nominations for Original Screenplay and Editing.

One of the top five films ever made.