Harry Potter has been shaped by its roots as a best-selling global literary phenomenon. From 1997-2007, Rowling’s publishing schedule gave her solitary control over the development of the narrative. The Warner Bros. film adaptations, 2001-11, developed alongside the books and often co-opted her authorial influence by emphasising Rowling’s creative input throughout the production process. Since the culmination of the seven-book, eight-film saga, however, Rowling has remained central to the franchise’s narrative and world-building initiatives. She is credited, for example, as co-creator of the original story for West End theatrical production Harry Potter and the Cursed Child (which extends the narrative beyond the epilogue of the books and films) and screenwriter for Fantastic Beasts and Where to Find Them (the five-film prequel saga that translates the wizarding world into 1920s New York, Paris, and beyond). The trademark ‘J.K. Rowling’s Wizarding World’ has been associated with all of these recent productions, indicating Rowling’s transition from literary author to multimedia brand guardian and content creator. Rowling is not only useful in constructing a sense of authenticity and artistry for new Potter projects, then; as an author – and authority – figure, she obscures the messy webs of commercial and creative relationships underpinning the continued success of the global transmedia phenomenon. Despite the reality of collaborative media authorship, Rowling’s voice is persistently the loudest. Her ability to frame meaning and value, and to mediate the ways in which fans engage with the franchise, has only grown stronger: she announced that Albus Dumbledore was gay at a 2007 book tour, but in 2016 she alters wizarding world canon in a single tweet. Rowling’s authorial evolution is arguably unique in the entertainment industry. Its closest corollary is perhaps George R. R. Martin, writing A Song of Ice and Fire alongside its TV adaptation A Game of Thrones; but where Martin relinquished details of the narrative to producers, Rowling’s involvement remains crucial to the sustained legitimacy of the Harry Potter – or, should I say, Wizarding World – franchise. It remains to be seen how this might develop in the years to come.