Solo: A Star Wars Story took just £7.6 million during its first five days on release, according to its distributors Disney.
It is the lowest amount made by any Star Wars film on its opening since the franchise was revived in the late 1990s.
The Last Jedi, released only five months ago, took £28.0 million across its four-day UK opening, while 2016's Rogue One notched up £17.3 million.
Solo has had positive reviews from critics, but its appearance in cinemas so soon after The Last Jedi may have damaged its chances of becoming a smash hit.
Warm weather over the bank holiday weekend could have affected ticket sales.
There is also the possibility that audiences are experiencing blockbuster fatigue.
Solo has been released just one week after Deadpool 2 (which took £13.0 million on its opening weekend) and a month after Avengers: Infinity War (£29.4 million).
The film traces the early years of Han Solo (played by Alden Ehrenreich) and is a spin-off from the main sequence of Star Wars movies.
According to figures from the British Film Institute, Solo's opening box office total of £7.6 million ranks below that for every Star Wars film for which comparable data is available.
This includes the three "prequels", which began in 1999 with The Phantom Menace.
Star Wars UK box office openings:
- The Force Awakens (2015): £34.0 million
- The Last Jedi (2017): £28.0 million
- Rogue One: A Star Wars Story (2016): £17.3 million
- Revenge of the Sith (2005): £14.4 million
- Attack of the Clones (2002): £11.4 million
- The Phantom Menace (1999): £9.8 million
- Solo: A Star Wars Story (2018): £7.6 million
(Figures not adjusted for inflation)