Memento is a 2000 American neo-noir psychological thriller film written and directed by Christopher Nolan, based on the short story "Memento Mori" by his brother Jonathan Nolan, which was later published in 2001. The film stars Guy Pearce, Carrie-Anne Moss, and Joe Pantoliano. The film follows Leonard Shelby (Pearce), a man who suffers from anterograde amnesia—resulting in short-term memory loss and the inability to form new memories—who uses an elaborate system of photographs, handwritten notes, and tattoos in an attempt to uncover the perpetrator who killed his wife and caused him to sustain the condition.

The film's non-linear narrative is presented as two different sequences of scenes interspersed during the film: a series in black-and-white that is shown chronologically, and a series of color sequences shown in reverse order (simulating for the audience the mental state of the protagonist). The two sequences meet at the end of the film, producing one complete and cohesive narrative.

Memento premiered at the Venice Film Festival on September 5, 2000, and was theatrically released in the United States on March 16, 2001. It was acclaimed by critics, who praised its nonlinear structure and themes of memory, perception, grief, and self-deception. It was also a commercial success, earning $40 million over its $9 million budget and gained a cult following. Memento received many accolades, including the Waldo Salt Screenwriting Award at the Sundance Film Festival, and Academy Award nominations for Best Original Screenplay and Best Film Editing. In 2017, the United States Library of Congress deemed the film "culturally, historically, or aesthetically significant" and selected it for preservation in the National Film Registry.