Margaret ( mar-gə-ret) is a 2011 American psychological drama film written and directed by Kenneth Lonergan. The film stars Anna Paquin, Jean Reno, Mark Ruffalo, J. Smith-Cameron, Jeannie Berlin, Allison Janney, Matt Damon, and Matthew Broderick. 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.

Although the studio insisted on a maximum 150-minute runtime, Lonergan's preferred version of Margaret was closer to three hours. Martin Scorsese and Thelma Schoonmaker contributed to editing a 165-minute version that Lonergan approved, but it was never released due to producer Gary Gilbert's refusal. Ultimately, Fox Searchlight Pictures released the 150-minute version in a limited U.S. release on September 30, 2011, to moderately positive reviews from critics. While some found it overlong, it appeared on several best-of-the-year lists. Lonergan completed a three-hour extended version with additional footage, a revised score and sound mix, which was released on DVD in July 2012. Critical praise has grown over time, and Margaret is now regarded as one of the 21st century's best films, ranking 31st in a BBC critics poll.

The film's title is derived from Gerard Manley Hopkins's poem "Spring and Fall: To a Young Child", which is analyzed in Lisa's English class. In the poem, the narrator addresses a young girl named Margaret, who mourns the falling autumn leaves as if they were deceased friends. The narrator informs Margaret that this sense of grief, though it feels profound, is an inescapable part of the human condition.