To celebrate the birthday, here are 43 photos of fans from premieres, book release events and gatherings over the last couple of decades.
London has an important place in Potter-lore, with King’s Cross station the departure point each year for the new school intake. Back to Hogwarts day returns on September 1, with fans set to gather at the station.
The city is, of course, home to Diagon Alley, accessible to members of the Wizarding World, and other Potter landmarks.
In the real world, London has welcomed millions of Harry Potter fans since the first book, Harry Potter and the Philosopher’s Stone, was released in 1997. Visitors can see Harry Potter & the Cursed Child, playing at the Palace Theatre in Shaftesbury Avenue, or visit filming locations of souvenir shops. The Warner Bros Studio Tour: The Making of Harry Potter is a short train ride away in Watford.
But here is a selection of photos taken primarily at premieres, launch events and celebrations of the world’s greatest young wizard, and his friends, teachers and adversaries.