Watchmen is an American comic book maxiseries by the British creative team of writer Alan Moore, artist Dave Gibbons and colorist John Higgins. It was published monthly by DC Comics in 1986 and 1987 before being collected in a single-volume edition in 1987. Watchmen originated from a story proposal Moore submitted to DC featuring superhero characters that the company had acquired from Charlton Comics. As Moore's proposed story would have left many of the characters unusable for future stories, managing editor Dick Giordano convinced Moore to create original characters instead.

Moore used the story as a means to reflect contemporary anxieties, to deconstruct and satirize the superhero concept and political commentary. Watchmen depicts an alternate history in which superheroes emerged in the 1940s and 1960s and their presence changed history so that the United States won the Vietnam War and the Watergate scandal was never exposed. In 1985, the country is edging toward World War III with the Soviet Union, freelance costumed vigilantes have been outlawed and most former superheroes are in retirement or working for the government. The story focuses on the protagonists' personal development and moral struggles as an investigation into the murder of a government-sponsored superhero pulls them out of retirement.

Gibbons used a nine-panel grid layout throughout the series and added recurring symbols such as a blood-stained smiley face. All but the last issue feature supplemental fictional documents that add to the series' backstory, and the narrative is intertwined with that of another story, an in-story pirate comic titled Tales of the Black Freighter, which one of the characters reads. Structured at times as a nonlinear narrative, the story skips through space, time and plot. In the same manner, entire scenes and dialogue have parallels with others through synchronicity, coincidence and repeated imagery.

A commercial success, Watchmen has received critical acclaim both in the comics and mainstream press. Watchmen was recognized in Time's List of the 100 Best Novels as one of the best English language novels published since 1923. In a retrospective review, the BBC's Nicholas Barber described it as "the moment comic books grew up". Moore opposed this idea, stating, "I tend to think that, no, comics hadn't grown up. There were a few titles that were more adult than people were used to. But the majority of comics titles were pretty much the same as they'd ever been. It wasn't comics growing up. I think it was more comics meeting the emotional age of the audience coming the other way."

After a number of attempts to adapt the series into a feature film, director Zack Snyder's Watchmen was released in 2009. A video game series, Watchmen: The End Is Nigh, was released in the same year to coincide with the film's release.

DC Comics published Before Watchmen, a series of nine prequel miniseries, in 2012, and Doomsday Clock, a 12-issue limited series and sequel to the original Watchmen series, from 2017 to 2019 – both without Moore's or Gibbons' involvement. The second series integrated the Watchmen characters within the DC Universe, home to more recognizable DC superheroes like Superman, Batman and Wonder Woman. A television continuation to the original comic, set 34 years after the comic's timeline, was broadcast on HBO from October to December 2019 with Gibbons' involvement. A comic continuation of the HBO series, titled Rorschach and written by Tom King, began publication in October 2020. Moore has expressed his displeasure with later adaptations and asked that Watchmen not be adapted for future works.