The Hogwarts Express leaves from platform 9¾ in J.K. Rowling’s Harry Potter series. The hidden platform is reached at London’s King’s Cross station by passing through the barrier between platforms 9 and 10.
Platform 9¾ is introduced when Harry travels to Hogwarts for the first time. Mrs. Weasley explains how to enter it, and Harry meets Ron Weasley while trying to find the correct platform. The location becomes one of the series’ recurring transitions between the ordinary and magical worlds.
King’s Cross station is a real London railway station, but the numbered platforms in the story do not match the exact arrangement shown in the films. A platform 9¾ shop and photo area were later established at the station as visitor attractions.
The fraction is part of the fictional platform’s name, not a train number. The Hogwarts Express itself is traditionally described as departing at 11 a.m. on 1 September.