Darkest Hour is a 2017 British war drama biographical film about Winston Churchill, played by Gary Oldman, in his early days as Prime Minister of the United Kingdom during the Second World War and the May 1940 war cabinet crisis, depicting his refusal to seek a peace treaty with Nazi Germany amid their advance into Western Europe. The film is directed by Joe Wright and written by Anthony McCarten. Along with Oldman, the cast includes Kristin Scott Thomas as Clementine Churchill, Lily James as Elizabeth Layton, Stephen Dillane as Viscount Halifax, Ronald Pickup as Neville Chamberlain, and Ben Mendelsohn as King George VI. The title of the film refers to a phrase describing the early days of the war, which has been widely attributed to Churchill.

The film had its world premiere at the 44th Telluride Film Festival on 1 September 2017, and it was also screened at the Toronto International Film Festival. It began a limited release in the United States on 22 November 2017, followed by general release on 22 December, and was released on 12 January 2018 in the United Kingdom. The film grossed $150 million worldwide and received positive reviews from critics, who particularly lauded Oldman's performance and deemed it one of the best of his career. Darkest Hour received several accolades, including Best Actor for Oldman at the Academy Awards. Oldman also won the BAFTA Award for Best Actor in a Leading Role, the Golden Globe Award for Best Actor – Motion Picture Drama, and the Screen Actors Guild Award for Outstanding Performance by a Male Actor in a Leading Role.