What was the first film for which J.K. Rowling wrote the screenplay?

The first film for which J.K. Rowling wrote the screenplay was Fantastic Beasts and Where to Find Them.

Released in 2016, the film expands the wizarding world beyond the Harry Potter story. Its central character is Newt Scamander, a magizoologist whose magical creatures escape in 1920s New York. Eddie Redmayne plays Newt, and David Yates directed the film.

Rowling had previously been credited as a producer on Harry Potter films, but Fantastic Beasts marked her screenwriting debut. She wrote the screenplay from an original story, using the title of a Hogwarts textbook and companion book associated with the fictional Newt Scamander.

The film began a planned series of Fantastic Beasts movies. Its later entries were The Crimes of Grindelwald and The Secrets of Dumbledore. Those titles should not be mistaken for Rowling’s first screenplay, which was the 2016 film.