A special Harry Potter train pulled into King's Cross Station to mark the film's release. A station manager admitted lots of children had already tried walking into a wall to find the imaginary 'platform nine and three quarters' which Harry uses to get to Hogwarts.
In the UK the movie has already broken the record for advance ticket sales when it previewed in some cinemas a week before its release.
In America J K Rowling's magical wizard story is set to top the previous opening weekend box-office record of £50m set by Jurassic Park II in 1997.
There, it's called Harry Potter and the Sorcerer's Stone and it'll be shown in about 3,500 screens.
Midnight screenings might be arranged to cope with demand.