Irréversible won the "Bronze Horse" award at the Stockholm Film Festival and was nominated for the Palme d'Or at the Cannes Film Festival, as well as the "Best Foreign Language Award" by the Film Critics Circle of Australia. It was also voted "Best Foreign Language Film" by the San Diego Film Critics Society (tied with Les Invasions Barbares).
Irréversible contains thirteen scenes, which are presented in reverse chronological order.
The beginning of the film (that is, the chronological end of the story) contains many distorted images and rapidly, freely moving, and rotating cameras that create a sense of chaos.
Two men, Marcus (Vincent Cassel) and Pierre (Albert Dupontel), are led out of a gay S&M nightclub, Club Rectum, by police. Earlier that evening, they arrived at the club in a frantic search for somebody nicknamed le Tenia (literally: the tapeworm). Marcus picks a fight with a man, incorrectly believing him to be le Tenia. When Marcus is pinned down by the man, who then snaps his arm and attempts to rape him, his friend Pierre rescues him by bludgeoning his attacker's face using a fire extinguisher, vividly crushing the man's skull.
In a succession of scenes, we learn that Marcus and Pierre went in search of le Tenia after questioning several prostitutes. A prostitute named Concha (a male transvestite whose real name is Guillermo Nuñez) accurately identifies the rapist as le Tenia after Marcus threatens to slash Concha with a piece of broken glass. Concha also reveals that the rapist is likely to be found at Club Rectum.
Marcus and Pierre were aided in their search by a man called Mourad and his friend, who promised to help them find le Tenia for money so Marcus could have his revenge. It is revealed that le Tenia raped Marcus's girlfriend Alex (Monica Bellucci), and placed her in a coma by repeatedly punching and kicking her in the head. The rape takes place after Alex encounters le Tenia beating Concha in a pedestrian underpass. Le Tenia then turns his attention on Alex and threatens her with a knife to her throat. The following anal rape scene is portrayed using a single, unbroken shot, lasting nine minutes.
From the rape scene it becomes clear that Pierre and Marcus attacked the wrong man. Le Tenia was standing right next to the man Pierre killed in Club Rectum.
In the next scene, we see Alex, Marcus and Pierre at a party. Alex is annoyed by Marcus's unrestrained use of drugs and alcohol.
The penultimate scene shows Marcus and Alex lying in bed after sex. Alex has a shower as they prepare to go to the party while Marcus goes out to buy wine. Alone, Alex discovers that she is pregnant.
The final scene shows Alex reading An Experiment with Time by John William Dunne in a park, surrounded by playing children. Beethoven's 7th Symphony sounds in the background. The camera spins around faster and faster, until it blacks out into a strobe effect and a roaring sound. A rapidly spinning image of a galaxy can be dimly perceived.
The final title card reads: LE TEMPS DETRUIT TOUT (Time Destroys Everything).
Film critic Roger Ebert has argued that the film's structure makes it inherently moral — that by presenting vengeance before the acts that inspire it, we are forced to process the vengeance first, and therefore think more deeply about its implications.
Audience reaction to both the lengthy, violent sexual attack and disquietingly brutal murder has ranged from appreciation of its artistic merit to leaving the theater in disgust. Newsweek magazine stated that this was the "most walked-out-of movie of the year.
The film also uses extremely low-frequency sound during the opening twenty to thirty minutes to create a state of disorientation and unease in the audience.