Production notes

After the acquisition of 21st Century Fox by The Walt Disney Company, 20th Century Fox confirmed at the 2019 CinemaCon that future Alien films were in development. In March 2022, it was reported that Fede Álvarez would write and direct a seventh Alien film after pitching his own story, said to be "unconnected" to the previous films in the franchise, with the project set to be released on Hulu. Álvarez later clarified that the film was not a standalone story. The film was said to take place between the events of Alien (1979) and Aliens (1986), with some technical crew members returning from the latter film. Álvarez stuck as close as possible to the established canon of the film series and used the fan wiki Xenopedia as a reference point while writing the story. The film features connections and references to all of the six prior Alien films—Alien, Aliens, Alien 3 (1992), Alien Resurrection (1997), Prometheus (2012), and Alien: Covenant (2017)—in some capacity, as well as the novel Alien: The Cold Forge (2018) by Alex White. In particular, the film ties directly to Alien and Prometheus, with Weyland-Yutani recovering the xenomorph that attacked Ellen Ripley in Alien from the USCSS Nostromo, an android named Rook who physically resembles Ash from the first film, and the "black goo" from Prometheus that gives birth to a human–xenomorph hybrid resembling an Engineer from Prometheus and the creature from the ending of Resurrection, and to The Cold Forge in Rook seeking to harvest the Plagiarus Praepotens (Z-01) from that novel to develop human immortality. Rook appears via an animatronic with the likeness of the late Ian Holm, who previously portrayed Ash. Álvarez confirmed the connections to Prometheus and stated that the hybrid's resemblance to the Engineers was intentional; this was done to bridge the gap between the prequels and the original films. The film also draws inspiration from the video game Alien: Isolation (2014). This involved integrating the emergency phone registration points from the game into the film's set design. These phones, which functioned as save points in the game, served as easter eggs that would foreshadow impending danger for the audience. The pregnancy of character Kay was inspired by Dina from The Last of Us Part II (2020), who would later be portrayed by the same actress, due to Álvarez playing the game while writing the film. The story centers on three pairs of siblings, whether blood relatives or found family.

By November 2022, Cailee Spaeny had entered negotiations to star. In March 2023, Isabela Merced was set to co-star opposite Spaeny. Later that month, David Jonsson, Archie Renaux, Spike Fearn, and Aileen Wu joined the cast. Renaux also auditioned for Jonsson's role and was secretly cast in December 2022; while Fearn was cast in February 2023 after two quick self tapes. Fearn initially tried to do an American accent but the director asked him to keep his own British accent.

Principal photography took place in Budapest from March 9 to July 3, 2023, utilizing unique locations including a working power plant for the Jackson's Star mining colony. Production designer Naaman Marshall aimed to reinterpret the Alien world while honoring the franchise's legacy, particularly the first two films in the series. As such, the Romulus section of the Renaissance space station was designed to be reminiscent of the set design seen in the film Alien and the video game Alien: Isolation, influenced by the original Alien concept art by Ron Cobb, as well as industrial heavy-lift machinery and vehicles. Meanwhile, the more advanced Remus section was designed to be reminiscent of the production design depicted in the film Aliens. Sets were built as enclosed spaces, with the cockpit of the Corbelan IV hauler built on a gimbal to simulate flight. The film was filmed chronologically and emphasized practical effects, using physical sets and creature designs to enhance realism. This approach focused on creating a tangible, immersive experience, contrasting with the heavier reliance on CGI in modern productions. To that end, effects companies Legacy Effects, Studio Gillis, and Wētā Workshop created the film's practical adult Xenomorphs, chestbursters and facehuggers, respectively, and the production would alternate between using animatronics, rod puppets or creature suits depending on the amount of movement required for the shot. The Xenomorph was made to more closely resemble H. R. Giger's original Alien design from the first film, rather than designs from the sequels. However the Xenomorphs' design was altered to feature serrated skin resembling that of a shark, to give the impression that someone could be cut just by touching it. Filmefex Studios created the prosthetic makeup for the actors as well as the film's dead bodies, while a sequence showing time lapse security footage of a rat being crushed and regenerated was stop motion animation created by Phil Tippett. One notable design element is the pulse rifle, which merges features from the original Alien flamethrower and the Aliens pulse rifle. This hybrid design reflects the film's intent to blend elements from both films, creating something familiar yet new. Cinematographer Galo Olivares shot the film using Arri Alexa 35 digital cameras with Arri Master Prime and Ultra Prime spherical lenses for a 2.39:1 widescreen aspect ratio. This was chosen to be a visual balance between Alien, which was shot using anamorphic lenses in a 2.39:1 aspect ratio, and Aliens, which was filmed using spherical lenses for a 1.85:1 aspect ratio. Olivares would begin filming scenes with wide angle lenses, and gradually switch to increasingly longer lenses as scenes became more intense, with a 75mm lens being the longest lens used. Álvarez selected an orange hue as the film's defining color, diverging from the blue tones of earlier "Alien" films. This choice aimed to give the film a distinct visual identity while maintaining a connection to the franchise's established aesthetic. Álvarez consulted Alien director Ridley Scott and Aliens director James Cameron during the film's production, who both expressed approval. However, Scott's comments two years after the film's release suggested otherwise.

The film's computer generated imagery was created by effects studios Industrial Light and Magic, Fin Design, Image Engine, Tippett Studio, Wētā FX, Wylie Co., Atomic Arts, and Metaphysic. Effects supervisor Nelson Sepulveda-Fauser said that Alvarez's emphasis on tangible elements built out of practical effects meant that "everything else that we needed to build in computer graphics had to work around that, and integrate into photography seamlessly.” For the Xenomorphs themselves, the digital versions were used for actions unfeasible with Legacy Effects's puppets — "we can’t get a practical creature of that size to perform some of the movements required for an action sequence" — with the motions being unsettling while not over-exaggerated, such as the Xenomorphs slowly crawling on walls. While the creature movements tried to mostly be close to the original films, the Facehuggers were faster and more fluid to overcome the technical limitations of the animatronic versions and make the scene more exciting. Two particularly complex effects were Navarro using an x-ray wand to discover a Chestburster, that required a reproduction of the character's internal anatomy, and the acid blood floating in zero gravity. Visual effects artist Ian Hunter created miniature effects for the film, in collaboration with the effects company Pro Machina and its founders Alec Gillis, Camille Balsamo-Gillis, and Reid Collums. This consisted of the spaceship Corbelan IV and the Weyland-Yutani Echo probe. These effects would be either filmed directly, or scanned into a computer for CGI modeling. Originally the miniatures were only designed to work as visual effect aids; however, the miniatures were eventually built, painted and finished by effects company Studio Gillis and shot in front of full screens and smoke. Filming of miniatures took place in Los Angeles to facilitate the required stage space, crew members and amenities.

Alien: Romulus grossed $105.3 million in the United States and Canada, and $245.5 million in other territories, for a worldwide total of $350.9 million. The film made $40 million from global IMAX, making it the highest-grossing horror film in the format. In the United States and Canada, Alien: Romulus was projected to gross $28–40 million in its opening weekend, with some estimates going as high as $45–55 million. The film made $18 million on its first day, including $6.5 million from Thursday night previews. It went on to debut to $42 million, topping the box office. The three-day opening included an estimated 2.7 million admissions and was the second-highest for the franchise and a record for director Fede Álvarez (beating the $26.4 million earned by 2016's Don't Breathe) and actress Cailee Spaeny (surpassing the $28.1 million earned by 2018's Pacific Rim Uprising). When asked about the biggest factors in watching the film, audiences polled by PostTrak listed the in-theater trailer (21%), online trailer (13%), and word of mouth (13%). In its second weekend, the film made $16.4 million, a drop of 61%, finishing behind holdover Deadpool & Wolverine. In just two weekends, the film became the second highest-grossing horror film in IMAX with $31.2 million, only behind Prometheus ($31.8 million). Outside the United States and Canada, the film made $68.1 million from international markets in its opening weekend for a global $110.1 million debut, which The New York Times listed as a success. Its international gross included $25.7 million from China, which Deadline Hollywood called an "over-performance". It was the second highest-grossing Hollywood film in China of the year with $110 million, behind Godzilla x Kong: The New Empire.

Alien: Romulus received positive reviews from critics. The review aggregator website Rotten Tomatoes reported that critics praised the film's "striking visuals and claustrophobic terror with gory action and a formidable lead performance from Cailee Spaeny", calling it "arguably the best installment since Aliens". On the website, 80% of 392 critics gave the film a positive review, with an average rating of 6.9/10. Its critics consensus reads: "Honoring its nightmarish predecessors while chestbursting at the seams with new frights of its own, Romulus injects some fresh acid blood into one of cinema's great horror franchises." According to Metacritic, the film received "generally favorable" reviews based on a weighted average score of 64 out of 100 from 57 critics. Audiences polled by CinemaScore gave the film an average grade of "B+" on an A+ to F scale, while those surveyed by PostTrak gave it an 82% positive score, with 65% saying they would definitely recommend it. Jordan Hoffman of Entertainment Weekly praised the film's direction, design, and writing, calling it "impressive, however, especially in how it looks like a new movie but is simpatico with the tech of the 1979 original" and deemed Spaeny "the finest weapon in the arsenal... differentiating herself quite a bit from the doe-eyed characters she played in Civil War and Priscilla. Her petite nature may not scream action hero, but, as has long been established, in space, no one can hear you scream anyway." Owen Gleiberman of Variety called Alien: Romulus "one of the best Alien sequels... It delivers the slimy creep-out goods in a way that none of the last three Alien films have." He further wrote that "Spaeny, with her clear eyes and serene resolve, makes her presence felt as Rain, the closest equivalent here to the fearless Ripley." James Mottram, in a five star review for NME, described the film as "thrilling and scary" and coming "close to the brilliance of Ridley Scott and James Cameron". He praised the production design, digital work, practical and visual effects and the score. Mottram described the performance of Jonsson as Andy as a "stand-out" a view shared by Clarisse Loughrey writing for The Independent. Mick LaSalle of the San Francisco Chronicle criticized the film, writing: "The first 45 minutes are boring beyond description. [...] The script has the aliens waking up and falling asleep at the convenience of the screenwriters, not in a way that makes consistent sense. [...] The foundational mistake came when someone said, 'Hey, let's make another Alien movie.' News flash: The alien concept is dead. Leave it alone, and leave poor Ian Holm out of it." David Ehrlich of Indiewire wrote: "The director would rather torture his cast than develop their characters. There's nothing inherently wrong with that trade-off, but Álvarez doesn't satisfy the first half of the equation well enough to justify his disregard for the second. High on jolts [...] and low on more probing scares, Romulus isn't nearly inventive enough to forefront its slaughter at the expense of its soul." Bilge Ebiri, writing for Vulture, expressed disappointment in the film's lessened ambition in comparison with other installments, stating that it is "a film engineered mostly to provide some basic genre thrills and keep the IP alive so that the now-Disney-owned Fox can generate more Alien movies.... Alien: Romulus is diverting enough, but it's also instantly forgettable—something I don't think I've ever said about any other Alien film, good or bad." In August 2026, Ridley Scott opined that, looking back on Alien: Romulus, he thinks the film "was OK", but could have been better. He thus saw it as a sign that the franchise "needs some help", hence his intentions to return to the property, which he announced to do so by rewriting the next Alien film.

The decision to digitally add the late Ian Holm for the character of Rook was widely criticized. Wendy Ide of The Guardian called it "a queasily misguided choice" that was "ghoulish, exploitative, disrespectful and unnecessary". In Slate, Sam Adams asked, "Why let the dead rest when there's IP [intellectual property] to be mined?" He went on to compare the film's studio to the franchise's villainous Weyland-Yutani corporation, in that it's "a massive conglomerate that puts profit ahead of respect for human lives". Loughrey called it "ethically problematic" and "cinematic necromancy" while Jesse Schedeen for IGN called it an "unforced error" that was "distractingly bad and completely unnecessary" and which almost ruined the movie. Similarly, SlashFilm reviewer Chris Evangelista wrote, "It's distracting and weird. It never, ever looks real [...] The simple truth here is that not only does this look bad, it's a bad idea all around". The Daily Telegraph critic Tim Robey commented, "One thing I never thought I'd complain about in 2024 was a film having too much Ian Holm in it". In response to the backlash, Álvarez compared the use of CGI to recreate Ian Holm's likeness to other actors' wearing prosthetics to portray historical figures, such as Gary Oldman as Winston Churchill in Darkest Hour: "I don't think Churchill wanted that, and I think that's worse, because that is them pretending to be them... This is not me pretending it's Ian Holm... It's just the makeup that makes it look like him." Álvarez told the Los Angeles Times that he had obtained permission from Holm's family, and stated it had been done to honor Holm's role in the franchise. Reviewer James Mottram praised the digital inclusion, saying that it "works well, both technically and narratively." The visual effects used to recreate Holm, which were incomplete for the theatrical release due to time constraints in post-production, were updated and fixed for the home video release. Álvarez said, "I convinced the studio we need to spend the money and make sure we give the companies that were involved in making it the proper time to finish it and do it right. It's so much better."