Production notes

In April 2015, Marvel Television was working with screenwriter John Ridley to craft a new television series for ABC, "reinventing" an existing Marvel Comics character or property. This was revealed years later to be the Eternals, a race of long-lived superheroes created by Jack Kirby. Ridley said he was trying to make a superhero series that viewers had not seen before, differentiating it from Marvel's other projects, and said his approach would have been a "really weird story" that may not have been entertaining for everyone. It ultimately did not move forward with Ridley, and Marvel Television was folded into Marvel Studios in December 2019.

Marvel Studios president Kevin Feige said in April 2018 that the studio was actively developing a film based on the Eternals, to be released as part of their Marvel Cinematic Universe (MCU) Phase Four slate of films. Marvel Studios had met with multiple screenwriters and was believed to be focusing on the character Sersi in the film. Marvel set Ryan and Kaz Firpo to write the script a month later, with their outline including a love story between the characters Sersi and Ikaris. The Firpos said the 1999 limited comic book series Earth X by Jim Krueger and John Paul Leon, which is about a dystopian version of the Marvel Universe, was a major inspiration for them. In June, Feige said Marvel was interested in exploring the "ancient aliens kind of sci-fi trope" by having the Eternals be the inspiration for myths and legends throughout the history of the MCU.

During late August, Marvel's director search for Eternals narrowed to a shortlist that included Chloé Zhao—who had also been in the running to direct Marvel's Black Widow (2021)—Nicole Kassell, Travis Knight, and the pair of Cristina Gallego and Ciro Guerra. Zhao approached Marvel Studios about making the film as she had been a fan of the MCU. She wanted to work with the studio to bring her own take and world-building to the franchise, and impressed them with a presentation that Feige described as fascinating, with "reams of visuals". Feige was also impressed with Zhao's passion for the project, since it was not a top priority for the studio. Zhao worked with producer Nate Moore to develop her pitch, noting she became interested in the project after reading its treatment that read like a Greek play "where gods get to discuss everything about human nature based on their own relationship". The presentation left Marvel concerned that she might take on a different big-studio project instead of Eternals, forcing them to move quickly to secure her, and Zhao was hired as director in September. This was ahead of her beginning production on her film Nomadland (2020), with Zhao beginning to work on the Eternals script during the filming of Nomadland. Zhao hoped to push the scope of the film further than Marvel's Avengers: Endgame (2019), but also wanted it to have intimacy. Zhao described the film as a melting pot of influences, taking from Kirby's original Eternals comics, Neil Gaiman's 2006 comic book run, previous MCU projects, and Zhao's love of science fiction and fantasy films and manga. Speaking specifically to her love of manga, she hoped those influences would create a "marriage of East and West". Zhao cited the television series Ancient Aliens (2009–present), the Final Fantasy video game franchise, concepts from Yuval Noah Harari's book Sapiens: A Brief History of Humankind (2011), and the films of Terrence Malick as inspirations.

Marvel saw Eternals as an opportunity to create an ensemble film that is not a crossover, similar to Guardians of the Galaxy (2014), and to introduce relatively unknown characters to audiences as they did with the Guardians and the Avengers. The studio also considered Eternals to be a perfect transition into its next phase of films along with projects such as Captain Marvel (2019), allowing them to cast a diverse group of actors to portray the various Eternals. Moore's initial planning documents for the project included the swapping of genders, sexualities, and ethnicities of some characters, and Zhao further advocated for this approach. In February 2019, Feige reiterated that Marvel was interested in the Eternals due to Kirby's epic, century-spanning story, with the film version covering 7,000 years and exploring humanity's place in the cosmos. Zhao said the Eternals "have lived among us for so long, [they have] the same struggles like identity, purpose, faith, personal freedom versus greater good—all the duality and flaws that make us human". With a story that spans so many years, the characters' relationships evolve like a complex family unit where friends "turn into frenemies, and then turn into enemies, and then come back to friendship". Zhao considered the Earth to be an eleventh character in the film.

Zhao continued working on a draft of the script throughout early 2019, which built upon the multiple drafts submitted by the Firpos. Approximately four months ahead of filming, the script was not finalized. Moore introduced Zhao to Patrick Burleigh, who had been part of Marvel's writers program, in the hopes that Burleigh could assist with the writing. Zhao hired him to work on the screenplay, which he did for about three months ahead of filming. Burleigh believed Zhao needed to write on the film as well as direct to "process the film through her own filter", and said her draft showed that she was "trying to make the Terrence Malick version of a Marvel film"; Zhao cited Malick's film The Tree of Life (2011) as a particular inspiration. Burleigh said his work on the script was mostly "structural" to find "the flow of the film", and likened the story to a road trip film.

Angelina Jolie joined the cast in March 2019, reportedly as Sersi, with Kumail Nanjiani and Don Lee cast in undisclosed roles the next month. At that time, the film was expected to feature Marvel Studios' first gay superhero. In May, Richard Madden entered negotiations for the role of Ikaris, and Salma Hayek had entered early negotiations for an undisclosed role the following month. In July, Variety reported that the cast included Jolie, Madden, and Millie Bobby Brown, but Brown denied that she had been cast.

At the 2019 San Diego Comic-Con, Feige officially announced The Eternals with a release date of November 6, 2020. He officially announced the casting of Jolie as Thena, Nanjiani as Kingo, Lee as Gilgamesh, Madden as Ikaris, and Hayek as Ajak, along with Lauren Ridloff as Makkari, Brian Tyree Henry as Phastos, and Lia McHugh as Sprite. Zhao looked for actors for each role that could "find a bit of themselves in their character". Feige added that one of these actors was portraying an LGBTQ character, with actor Haaz Sleiman later revealing that Phastos is depicted as gay in the film. Sleiman portrays the character's husband, and the pair have a child in the film. Sleiman felt it was important to depict "how loving and beautiful a queer family can be" rather than the "sexual or rebellious" depiction in some previous media. Feige said the relationship was "always sort of inherent in the story" and he felt it was "extremely well done" in the film, while Sleiman said it was a "thoughtful" depiction.

Eternals is set around eight months after the events of Avengers: Endgame, and addresses why the Eternals did not interfere in any previous conflicts in the MCU. Both Feige and Moore said the film would have "major ripple effects" on the future of the MCU, and at times, it was "a challenge" to balance the grounded nature of the MCU with the "mythic grandeur" of the Eternals property.

By the time of the film's official announcement in July 2019, principal photography had begun at Pinewood Studios in Buckinghamshire, England. Ben Davis served as director of photography, after doing so on several previous MCU films. Zhao said Marvel Studios allowed her creative freedom to shoot the film on location, "exactly the way [she] wanted to shoot" it. She was able to use a similar style to her previous films, including 360° shots and working with the same camera and rigs as were used for her film Nomadland (2020), which Zhao was set to complete back-to-back with Eternals. Zhao felt that she "got lucky in that Marvel wants to take risks and do something different". Zhao cited The Revenant (2015) as a primary influence when composing the film's action sequences.

Gemma Chan and Barry Keoghan were in talks to join the cast in August 2019. Chan previously portrayed Minn-Erva in Captain Marvel, but reports noted that she was potentially being looked at by Marvel to play a separate character in this film. Since Minn-Erva dies in that film, Chan had felt that it was unlikely she would return to the MCU, but after working on the film she was told by Feige that the studio wanted to "make better use" of her in a future project. This led to Chan auditioning for Sersi, one of the last actresses to be considered for the role. Chan later described Sersi as the most difficult role for the film to cast. Chan and Keoghan were confirmed to be cast in the film at the D23 Expo in August, in the roles of Sersi and Druig, respectively, along with Kit Harington as Dane Whitman. Chan said she and Marvel Studios were surprised by how soon after Captain Marvel her new MCU role came, with both assuming that it would have been a project further in the future. Harish Patel was cast at the end of August as Karun, Kingo's manager, and filmed his role from September 2019 until January 2020.

By early November, filming had taken place in the Canary Islands. The cast and crew, including Jolie and Madden, had to be evacuated from a shooting location on the island of Fuerteventura when an explosive device, thought to be a remnant armament from a Nazi base, was found there. Later that month, Zain Al Rafeea joined the cast. In early January 2020, filming took place outside the Oxford University Museum of Natural History in Oxford, England, as well as Hampstead Heath and in Camden in London, under the working title Sack Lunch. Chan said the filming process felt very different from what she experienced on Captain Marvel, explaining that Eternals shot more on location and used natural light while Captain Marvel had more studio work and bluescreens. Filming wrapped on February 4, 2020.

In March 2020, Scanline VFX, one of the companies working on the film's visual effects, confirmed that they would be working remotely due to the COVID-19 pandemic. Industrial Light & Magic, Luma Pictures, RISE, and Weta Digital also worked on the film's visual effects. In early April, Disney shifted much of their Phase Four slate of films due to the pandemic, moving The Eternals' release date to February 12, 2021. In August, the film's title was officially shortened from The Eternals to Eternals, and the next month, the release date was pushed back to November 5, 2021. Reshoots had taken place by mid-November 2020.

Additional filming occurred in Los Angeles in early February, also under the working title Sack Lunch. Dylan Tichenor and Craig Wood serve as co-editors of the film. Tichenor said Zhao usually edits her own films and has "strong opinions", but on Eternals she was relying on Tichenor and Wood due to the size of the production and the ongoing awards season for Nomadland. Tichenor added that Zhao respected the pair's editing experience and point of view, and they made their first cut of the film without much input from her. They began adjusting the film based on Zhao's feedback and were still working on the editing in April 2021. At the end of the month, Zhao said editing for the film was in its "final stretch", and Jashaun St. John was revealed to appear in the film, after previously starring in Zhao's film Songs My Brothers Taught Me (2015).

At the end of May 2021, with the release of the first teaser trailer and poster for the film, the official writing credits were revealed: Zhao was credited as the screenwriter, both as a solo contributor and as part of a writing team with Burleigh, while Ryan and Kaz Firpo received story credit. Additionally, Gil Birmingham was revealed to have been cast in the film, although he was absent in the final film. In July 2021, Writers Guild of America West presented the film's final writing credits, awarding Ryan and Kaz Firpo screenplay credit along with Zhao and the team of Zhao and Burleigh, in addition to their story credit. Moore believed the studio had "bit off as much as we could chew" with the film, creating one that "felt urgent and present and had [a fast] pace, but also took time to reflect back over the centuries".

At the film's world premiere, Matt Donnelly of Variety tweeted that Harry Styles made an appearance in a post-credits scene as Eros / Starfox, Thanos's brother in the comics, which was not shown in early press screenings of the film. Zhao later revealed that she "kept tabs on [Styles]" since his appearance in the film Dunkirk (2017), believing that he "makes me think of Eros as a character". WWE wrestler Becky Lynch had a role in the film for a planned post-credits scene that was intended to set up a future project. The scene was removed for being reportedly "too depressing".

Eternals grossed $164.9 million in the United States and Canada, and $237.2 million in other territories, for a worldwide total of $402.1 million. The film's opening weekend earned $162 million globally, which was the second-largest worldwide opening weekend in the COVID-19 pandemic for a Hollywood film, of which IMAX contributed to over $13.6 million.

Advanced ticket sales for Eternals were estimated to be $2.6 million in its first 24 hours, outpacing those for Shang-Chi and the Legend of the Ten Rings ($1.4 million) and Black Widow ($2 million) during the same time frame, while AMC Theatres had the largest first-day sales of 2021 for the film. In November, Fandango reported that pre-sales for Eternals were the second-largest of 2021, behind Black Widow. In October, Boxoffice Pro initially projected that the film would earn $82–102 million within its opening weekend, and around $210–280 million in total domestic box office. At the end of the month, Boxoffice Pro modified their projections to $67–92 million for the film's opening weekend, and around $165–215 million in total domestic box office, due to mixed early critical reception. According to Deadline Hollywood, Eternals was expected to earn $75 million within its domestic opening weekend, and around $150 million globally.

In the United States and Canada, Eternals earned $30.7 million on its opening day, which included $9.5 million from Thursday night previews, marking the third-largest opening day of the pandemic, behind Black Widow and Venom: Let There Be Carnage. Its opening weekend earned $71.3 million from 5.5 million theater admissions, making it the top film of the weekend. IMAX accounted for over $7.6 million over the weekend. This marked the fourth-largest opening weekend of the pandemic. The domestic opening weekend gross was lower than various pre-release projections. Deadline attributed this to the film's overall mixed reception from critics and audiences. In its second weekend, Eternals remained the top film, grossing over $27.5 million. Eternals became the sixth-highest-grossing film of 2021 in the United States.

Outside of North America, Eternals earned over $90.7 million within its opening weekend from 46 markets. It was number one in nearly all of these markets. The international opening weekend gross had exceeded various pre-release projections. IMAX contributed to $6 million of the opening gross, from 58 countries. The film scored the largest opening of the pandemic in Italy, Brazil, and Hong Kong. In South Korea, Eternals earned $14.4 million, marking the largest debut for a Hollywood film amid the pandemic. In Russia, the film earned an opening of $5.4 million through six days. In its second weekend, Eternals earned $48 million from 49 markets, a drop of 49%. It remained number one in many of these territories. The following weekend, the film earned $22.7 million. It was the top film of the weekend internationally, remaining the top film in many territories, including all markets across Latin America, except for Mexico. As of November 28, 2021, the film's largest markets were South Korea ($26.4 million), the United Kingdom ($18.7 million), France ($14.9 million), Mexico ($14.3 million), and Brazil ($11.1 million).

The review aggregator Rotten Tomatoes reports an approval rating of 48% based on 416 reviews, with an average rating of 5.7/10. The website's critical consensus reads, "An ambitious superhero epic that soars as often as it strains, Eternals takes the MCU in intriguing—and occasionally confounding—new directions." On Metacritic, the film has a weighted average score of 52 out of 100, based on 62 critics, indicating "mixed or average" reviews. Upon release, it became the lowest-rated MCU film on both websites and the first installment to be classified as "rotten" on Rotten Tomatoes. Audiences polled by CinemaScore gave the film an average grade of "B" on an A+ to F scale, the lowest grade for an MCU film at the time of its release, and PostTrak reported 78% of audience members gave it a positive score, with 60% saying they would definitely recommend it.

Charlotte O'Sullivan of the Evening Standard described the film as "lavish" and "ambitious", and praised the fight sequences as "astounding, beautifully paced and crammed with detail". Robert Abele of TheWrap commended the cinematography and felt "an earnestness to the operatic stakes". Oliver Jones of the Observer called it "full of wonder and romance and fueled by an agenda and audacity all its own". Owen Gleiberman was disappointed over Zhao's missing filmmaking style that shaped her films The Rider (2017) and Nomadland (2020) to "embrace the straight-up expository conventionality of Marvel filmmaking", but felt that the film was a "squarely fun and gratifying watch". Moira Macdonald of The Seattle Times thought "it's got some pretty slow spots midfilm and it's desperately in need of a bit more wit ... what it does have is a palpable, artful mood; this is a movie full of superheroes who spend time thinking and feeling, and of special effects that aren't just zippy but often delicately elegant".

Linda Marric of The Jewish Chronicle described it as "a mishmash of well-meaning, yet jarringly verbose and bafflingly incoherent nonsense which is only just about saved by some half decent performances"; Nicholas Barber of BBC Culture called Zhao's direction "workmanlike"; and Clarisse Loughrey of The Independent said that it "strives for the same expansive soulfulness" as Nomadland "but discovers there's room enough only for the occasional burst of it". Brian Truitt of USA Today praised Zhao's "penchant for naturalistic environments", but wrote that the narrative "struggles to juggle its many subplots and tries to do too much". Mark Kennedy of the Associated Press criticized the dialogue and fight scenes, but praised the visual effects and Nanjiani's performance. Shirley Li of The Atlantic felt that "Zhao's delicate examination of her characters outshines Eternals' duller and more convoluted moments".

Robbie Collin wrote the film was "constantly engaged in a kind of grit-toothed authenticity theatre, going out of its way to show you it's doing all the things proper cinema does, even though none of them bring any discernible benefit"; Kevin Maher felt "a strange self-sabotaging energy at the heart"; and Steve Rose of The Guardian missed "the breezy wit of Marvel's best movies ... like coming into Avengers: Endgame cold without having seen any of the preceding installments". K. Austin Collins of Rolling Stone felt that the film was "good at telling us where to look, at impressing us with its manufactured sense of grandeur", but lacked "any credible sense of what's actually worth seeing". Justin Chang of the Los Angeles Times had a "depressing realization that you've just seen one of the more interesting movies Marvel will ever make, and hopefully the least interesting one Chloé Zhao will ever make". Brian Lowry of CNN thought "the movie's structural flaws offset its stunning visuals and strong performances". Kyle Smith of National Review was harsher, describing it as "one of the dumbest, cheesiest, most trite, and least human" of the MCU films.

The mixed reception surprised some commentators, given the MCU's positive track record and the acclaim of Zhao's previous work. Richard Newby of The Hollywood Reporter wrote that "much of the criticism of Kirby's work", which was divisive for its subject matter and relationship to the wider Marvel Universe, "has followed Zhao in her adaptation." He compared the divided response to that of Zack Snyder's DC Extended Universe (DCEU) films Man of Steel and Batman v Superman: Dawn of Justice (2016), writing that they and Eternals share "a deconstructive approach to superheroes and force them to question their purpose in the world, through meditative and melancholy narrative beats, and a tragic yet hopeful ending." This approach, he felt, subverted critics' and audiences' expectations, which made them review the film more harshly. Zhao addressed some of the criticisms of the film, believing some of the division came from everyone "having an existential crisis" because of the COVID-19 pandemic and the film being an "existential crisis, both for humanity and God". She also felt the reactions to how the film incorporated her filmmaking sensibilities with Marvel's were "a testament to how much we had merged with each other; how uncomfortable that might make people feel".

The film was given the Seal of Authentic Representation from the Ruderman Family Foundation for Ridloff's role as Makkari. The seal is given to films and series that feature actors with disabilities who have at least five lines of dialogue. Eternals was also one of 28 films that received the ReFrame Stamp for 2021, awarded by the gender equity coalition ReFrame for films that are proven to have gender-balanced hiring.