Platform Nine and Three-Quarters

• Type: Magical Train Platform
• Location: King's Cross Station, London, England
• Owner/Residents: Maintained by the Ministry of Magic for use by the wizarding community.
• Key Features: Concealed magical gateway, departure and arrival point for the Hogwarts Express, accessible only to witches and wizards.

Platform Nine and Three-Quarters is a magical platform located at the Muggle King's Cross Station in London. It is the departure point for the Hogwarts Express, the train that transports students to and from Hogwarts School of Witchcraft and Wizardry at the beginning and end of each term. To access the platform, a witch or wizard must walk directly through the seemingly solid brick barrier dividing platforms nine and ten. The barrier acts as a magical portal, allowing magical folk to pass through seamlessly while remaining unnoticed by the surrounding Muggles. From the other side, the platform appears much like a standard old-fashioned railway station, featuring a wrought-iron archway overhead bearing the words Platform Nine and Three-Quarters. The platform is typically bustling with students and their families, who are seen with trunks, owl cages, and other magical luggage. The iconic scarlet steam engine of the Hogwarts Express is the central feature, waiting to begin its journey north to Hogsmeade Station. The use of a single, discreet departure point for the Hogwarts Express was established by the Ministry of Magic to provide a secure and orderly method for hundreds of students to travel to Hogwarts without attracting Muggle attention. This method was instituted in the 19th century after various prior methods, such as Portkeys and unregulated travel, proved chaotic and breached the International Statute of Secrecy (Pottermore).

Platform Nine and Three-Quarters serves as a crucial transitional space and a recurring setting for significant moments throughout the series. It is the symbolic gateway between Harry Potter's mundane life with the Dursleys and his true home in the magical world.

• In Harry Potter and the Philosopher's Stone, the platform is Harry's first true test of entering the wizarding world on his own. Lost and confused, he is aided by the Weasley family, initiating his lifelong friendships with Ron Weasley and the rest of the family.
• In Harry Potter and the Chamber of Secrets, Dobby the house-elf magically seals the barrier, preventing Harry and Ron from passing through. This act forces them to fly Arthur Weasley's enchanted Ford Anglia to school, leading to significant consequences.
• In Harry Potter and the Order of the Phoenix, Sirius Black, in his Animagus form as a large black dog, accompanies Harry to the station, a risky farewell that underscores their close bond.
• In the epilogue of Harry Potter and the Deathly Hallows, the platform is the setting for the final scene of the series. Nineteen years after the Battle of Hogwarts, an adult Harry, Ginny Weasley, Ron Weasley, and Hermione Granger are present to see their own children, including Albus Severus Potter, off on the Hogwarts Express. This brings the story full circle, ending where Harry's journey truly began.

• The Barrier: The magical entrance to the platform, located between the Muggle platforms nine and ten. It appears as a solid brick wall to non-magical people but is permeable to witches and wizards.
• The Platform: The main waiting area where students, families, and pets gather before the train's departure. It is here that the scarlet Hogwarts Express waits.

• J.K. Rowling has stated that she chose King's Cross Station because her parents met on a train from King's Cross to Arbroath, Scotland, giving the location personal significance. She has also admitted that she may have been mentally picturing Euston Station, as King's Cross does not have platforms nine and ten adjacent to each other in the way described in the book (J.K. Rowling interview).
• In the film adaptations, the entrance to the platform is depicted as a large, solid brick archway between the platforms, rather than the ticket barrier described in the novel (film).
• A permanent tourist attraction has been installed at the real King's Cross Station in London, featuring a luggage trolley halfway through a wall under a “Platform 9 ¾” sign, allowing fans to take photos.