Director Fede Alvarez sought out special effects crew from Aliens (1986) to work on the creatures. Physical sets, practical creatures, and miniatures were used wherever possible to help ground later VFX work.
The idea of an Alien film centering on younger characters was inspired by a deleted scene from Aliens (1986) that was later restored in the Special Edition. Fede Alvarez explained, "There's a moment where you see a bunch of kids running around the corridors of this colony. And I thought, 'Wow, what would it be like for those kids to grow up in a colony that still needs another 50 years to terraform?' So I remember thinking, 'If I ever tell a story in that world, I would definitely be interested in those kids when they reach their early twenties.'"
The film was originally scheduled to be released on Hulu, but it switched to a theatrical release in June 2023.
After months of speculation about the meaning of the subtitle 'Romulus', writer/director Fede Alvarez explained that it refers to the Romulus space station where part of the action in the film takes place. He also implied that there is a sister station called 'Remus', so both structures are named after the twins Romulus and Remus, the mythological founders of the city of Rome and the Roman kingdom. This continues the franchise tradition of naming entities after characters or places from classic mythology, such as: the ship Prometheus from Prometheus (2012) (named after a Greek Titan); the ship Anesidora and the APOLLO computer from Alien: Isolation (2014) (named after a Roman goddess and god respectively); the planetoid Acheron from Aliens (1986) (named after a river in the Greek underworld); and the USS Auriga from Alien: Resurrection (1997) (named after a Greek hero).