Watchmen is a 2009 American superhero film based on the 1986–1987 DC Comics limited series of the same name co-created and illustrated by Dave Gibbons (with co-creator and author Alan Moore choosing to remain uncredited). Directed by Zack Snyder from a screenplay by David Hayter and Alex Tse, the film features Malin Åkerman, Billy Crudup, Matthew Goode, Carla Gugino, Jackie Earle Haley, Jeffrey Dean Morgan, and Patrick Wilson. A dark and dystopian deconstruction of the superhero genre, the film is set in an alternate history in the year 1985 at the height of the Cold War, as a group of mostly retired American superheroes investigate the murder of one of their own before uncovering an elaborate and deadly conspiracy with which they are all connected.

For nearly two decades from October 1987 until October 2005, a live-action film adaptation of the Watchmen series became stranded in development hell. Producers Lawrence Gordon and Joel Silver began developing the project at 20th Century Fox, later moving it to Warner Bros. Pictures, the sister company of Watchmen publisher DC Comics, and hiring director Terry Gilliam, who eventually left the production and deemed the complex comic "unfilmable". During the 2000s, Gordon and Lloyd Levin collaborated with Universal Pictures, Revolution Studios and Paramount Pictures to produce the film. Directors David Hayter, Darren Aronofsky, and Paul Greengrass were attached to the project before it was canceled over budget disputes. In October 2005, the project returned to Warner Bros., where Snyder was hired to direct. Paramount remained as its international distributor, whereas Warner Bros. would distribute the film in the United States. However, Fox sued Warner Bros. for copyright violation arising from Gordon's failure to pay a buy-out in 1991, which enabled him to develop the film at the other studios. Fox and Warner Bros. settled this before the film's release, with Fox receiving a portion of the gross. Principal photography began in Vancouver, in September 2007. As with his previous film 300 (2006), Snyder closely modeled his storyboards on the comic but chose not to shoot all of Watchmen using green screens and opted for real sets instead.

Following its world premiere at Odeon Leicester Square on February 23, 2009, the film was released in both conventional and IMAX theatres on March 6, 2009. The film underperformed at the box office, grossing over $185.4 million worldwide against a production budget between $130–138 million; however, the film later found financial success at the home media markets. Greg Silverman (former Warner Bros. executive) said that the film did later become profitable.

The film received mixed to positive reviews from fans and critics; the style was praised, but Snyder was accused of making an action film that lacked the thematic depth and nuance of the comic. Over the years, it had gained a cult following. A DVD based on elements of the Watchmen universe was released, including an animated adaptation of the Tales of the Black Freighter comic within the story voiced by Gerard Butler and a fictional documentary titled Under the Hood detailing the older generation of superheroes from the film's backstory. A director's cut with 24 minutes of additional footage was released in July 2009. The "Ultimate Cut" edition incorporated the animated comic Tales of the Black Freighter into the narrative as it was in the original graphic novel, lengthening the runtime to 3 hours and 35 minutes, and was released on November 10, 2009. The director's cut was better received than the theatrical release.