Black Swan is a 2010 American psychological horror film directed by Darren Aronofsky from a screenplay by Mark Heyman, John McLaughlin, and Andres Heinz, based on a story by Heinz. The film stars Natalie Portman in the lead role, with Vincent Cassel, Mila Kunis, Barbara Hershey, and Winona Ryder in supporting roles. The plot revolves around a production of Tchaikovsky's Swan Lake by the company of New York City Ballet. The production requires a ballerina to play the innocent and fragile White Swan, for which the committed dancer Nina Sayers (Portman) is a perfect fit, as well as the dark and sensual Black Swan, which are qualities better embodied by the new rival Lily (Kunis). Nina is overwhelmed by a feeling of immense pressure when she finds herself competing for the role, causing her to lose her tenuous grip on reality and descend into madness.

Aronofsky conceived the premise by connecting his viewings of a production of Swan Lake with an unrealized screenplay about understudies and the notion of being haunted by a double, similar to the folklore surrounding doppelgängers. Aronofsky cites Fyodor Dostoevsky's The Double as another inspiration for the film. Aronofsky also considered Black Swan a companion piece to his film The Wrestler (2008), with both films revolving around demanding performances for different kinds of art. He and Portman first discussed the project in 2000, and after a brief attachment to Universal Pictures, Black Swan was produced in New York City in 2009 by Fox Searchlight Pictures. Portman and Kunis trained in ballet for several months prior to filming.

Black Swan premiered at the 67th Venice International Film Festival on September 1, 2010, and had a limited release in the United States starting on December 3, before opening in wide release on December 17. Upon release, the film received positive reviews from critics, with praise toward Aronofsky's direction and the performances of Portman, Kunis, and Hershey. It also emerged as a major commercial success at the box-office, grossing $329 million worldwide on a $13 million budget. The film received five nominations at the 83rd Academy Awards, including Best Picture and Best Director (Aronofsky), with Portman winning Best Actress; it also received four nominations at the 68th Golden Globe Awards, including Best Motion Picture – Drama and Best Director (Aronofsky), with Portman winning Best Actress in a Motion Picture – Drama. In 2021, Portman's performance was included in The New Yorker's list of the best film performances of the 21st century.