Fahrenheit 9/11 is a 2004 American documentary film directed and written by, and starring filmmaker, director, political commentator and activist Michael Moore. The subjects of the film are the presidency of George W. Bush, the Iraq War, and the media's coverage of the war. In the film, Moore states that American corporate media were cheerleaders for the 2003 invasion of Iraq, and did not provide an accurate or objective analysis of the rationale for the war and the resulting casualties there.

The title of the film alludes to Ray Bradbury's 1953 novel Fahrenheit 451, a dystopian view of the future United States, drawing an analogy between the autoignition temperature of paper and the date of the September 11 attacks; one of the film's taglines was "The Temperature at Which Freedom Burns".

The film debuted at the 2004 Cannes Film Festival, where it was awarded the Palme d'Or, the festival's highest award. It received generally positive reviews from critics, but it also generated intense controversy, particularly including disputes over its accuracy. The film became the highest-grossing documentary of all time, grossing over $220 million (although it was later surpassed by Michael Jackson's This Is It in 2009). A follow-up, titled Fahrenheit 11/9, about the presidency of Donald Trump, was released in September 2018.