In J.K. Rowling’s fantasy novel Harry Potter and the Philosopher’s Stone, Hogwarts Express passengers use Platform 9¾ at King’s Cross Station.
The platform is hidden from ordinary railway passengers between platforms 9 and 10. Harry learns about it when the Weasley family explains that witches and wizards must run directly at the barrier between the platforms. The magical entrance leads to the scarlet steam train bound for Hogwarts School of Witchcraft and Wizardry.
Harry boards the train for the first time on 1 September, the traditional start of the Hogwarts school year. The platform becomes a recurring location throughout the series, serving as both a departure point and a place where students return to London after term.
The fraction is written with the three-quarter symbol in the books and is commonly rendered as “9¾.” It is not the same as a conventional platform number. King’s Cross also contains a real commemorative trolley installation associated with the fictional platform.