Manchester by the Sea is a 2016 American drama film written and directed by Kenneth Lonergan that stars Casey Affleck, Michelle Williams, Kyle Chandler, and Lucas Hedges. Revolving around the themes of depression, guilt, grief, responsibility, dysfunctional families, and post-traumatic stress disorder, the plot follows a depressed and grief-stricken man who becomes the legal guardian of his teenage nephew after the death of his brother.

The film premiered at the Sundance Film Festival on January 23, 2016, and was picked up by Amazon Studios for distribution. Manchester by the Sea was filmed during March and April 2015 in the eponymous Massachusetts town and other towns in the state, such as Beverly, Essex, Gloucester, Swampscott, Lynn, Middleton, Tewksbury, and Salem. It began a limited release on November 18, 2016, before a wide release on December 16, 2016. It grossed $79 million worldwide against a budget of $9 million.

The film received critical acclaim and was widely counted among the best films of 2016; the National Board of Review listed it as the top film of 2016. Critics complimented the performances of Affleck, Hedges, and Williams, as well as Lonergan's screenplay and direction. At the 89th Academy Awards, Manchester by the Sea won Academy Awards for Best Actor for Affleck and Best Original Screenplay, and additional nominations for Best Picture, Best Director, Best Supporting Actor (Hedges), and Best Supporting Actress (Williams). Affleck also won the Golden Globe Award for Best Actor – Motion Picture Drama; the film was also nominated in four other categories. The British Academy Film Awards nominated the picture for six awards, of which it won Best Actor in a Leading Role for Affleck and Best Original Screenplay. Since then, it has been considered to be among the best films of the 21st century.