Margaret ( mar-gə-ret) is a 2011 American epic psychological drama film written and directed by Kenneth Lonergan. The film stars Anna Paquin, Jean Reno, Matt Damon, Mark Ruffalo, J. Smith-Cameron, Jeannie Berlin, Allison Janney, Matthew Broderick, Kieran Culkin, Olivia Thirlby, and Rosemarie DeWitt. Margaret was filmed in 2005 and originally scheduled for release that year by Fox Searchlight Pictures, but was repeatedly delayed while Lonergan struggled to create a final cut he was satisfied with, resulting in multiple lawsuits. The litigation ended in 2014.

While the studio insisted the film's running time could not exceed 150 minutes, Lonergan's preferred version was closer to three hours. Martin Scorsese and Thelma Schoonmaker contributed to editing a 165-minute version that Lonergan approved; the cut was never released because producer Gary Gilbert refused to approve it. Eventually, Fox Searchlight Pictures released the 150-minute film in a limited release in the United States on September 30, 2011, to moderately positive reviews from critics. Some considered it overlong, but it was praised for its acting and later appeared in several publications' lists of the year's best films. Critical praise has grown over time, and Margaret is now regarded as one of the best films of the 2000s and of the 21st century, and was ranked 31st in a BBC critics poll of the 21st century's 100 greatest films.

Lonergan completed a three-hour extended version incorporating extra footage with a revised score and sound mix, which was released on DVD in July 2012.

The title of the film comes from the Gerard Manley Hopkins poem “Spring and Fall: To a Young Child,” which is discussed in Lisa's English class. In the poem, the narrator speaks to a young girl named Margaret, who is grieving the death of autumn leaves as if they were dying friends. The narrator explains to Margaret that this grief, although it feels profound, is an inescapable part of the human condition.