Doomsday Clock is a 2017–2019 superhero comic book limited series published by DC Comics, written by Geoff Johns with art by penciller Gary Frank and colorist Brad Anderson. The series concludes a tangential story established in the New 52 and DC Rebirth, and it is a sequel to the 1986–1987 graphic novel Watchmen by Alan Moore, Dave Gibbons and John Higgins, making it the first official crossover between Watchmen and the mainstream DC Universe.

At the time, DC co-publisher Dan DiDio promoted Doomsday Clock as an official "sequel" to Watchmen. However, series writer and DC Chief Creative Officer Geoff Johns declined to characterize it as such, viewing it as a "standalone" story.

The series's debut issue was published on November 22, 2017, and the final issue was published on December 18, 2019.

Doomsday Clock is part of the DC Rebirth initiative, and it continues the narrative that was established with the 2016 one-shot DC Universe: Rebirth #1, the 2017 crossover event "The Button" and other related stories. It is a follow-up to the 1986–1987 miniseries Watchmen by Alan Moore, Dave Gibbons and John Higgins, and it introduces that story's characters into the DC Universe, alongside a few original characters created for the book. Although Dan DiDio (then DC's co-publisher) confirmed that it is a sequel to that miniseries, Johns originally declined to characterize it as such, viewing it as a standalone story, saying, "It is something else. It is Watchmen colliding with the DC Universe."

Doomsday Clock was revealed on May 14, 2017, with a teaser image displaying the Superman logo in the 12 o'clock slot of the clock depicted in Watchmen and the series title in the bold typeface used for Watchmen.

The story includes many characters, but it has a particular focus on Superman and Doctor Manhattan. Johns felt like there was an interesting story to be told in DC Rebirth with Doctor Manhattan; he thought there was an interesting dichotomy between Superman—an alien who embodies and is compassionate for humanity—and Doctor Manhattan—a human who has detached himself from humanity. This idea led to over six months of debates amongst the creative team about whether or not to intersect the Watchmen universe with the DC Universe. He explained that Doomsday Clock was the "most personal and most epic, utterly mind-bending project" that he had worked on in his career.

Johns also explained that Doomsday Clock is a stand-alone story with no tie-in material. However, it "will have an impact on the entire DC Universe. It will affect everything moving forward and everything that has come before. It will touch the thematic and literal essence of DC." So by the time the final issue is released, "the rest of the universe will have caught up to it — and the repercussions of the event will become known."

The first issue of Doomsday Clock was released on November 22, 2017, with a planned run of 12 issues. The series was scheduled to release monthly and end in December 2018, with planned breaks in March and August 2018. However, in January 2018, it was announced that the series would take a break in March and April 2018, before releasing again in May 2018 and switching to a bi-monthly schedule, with the series ending in July 2019. Issue #8 was pushed back from November 28 to December 5, 2018. Issue #9 was pushed back from January 23 to March 6, 2019. Issue #10 was pushed back from March 27 to May 29, 2019. Issue #11 was pushed back from May 22 to September 4, 2019. The twelfth and final issue was published on December 18, 2019.