What was the first Harry Potter story J.K. Rowling wrote as a screenplay?

The first Harry Potter story J.K. Rowling wrote as a screenplay was Fantastic Beasts and Where to Find Them.

Published as a screenplay in 2016, Fantastic Beasts and Where to Find Them expanded a textbook title mentioned in the Harry Potter novels into a new story set in the wizarding world. The film premiered in London on 8 November 2016 and was released internationally later that month.

The story follows magizoologist Newt Scamander in 1926 New York, where magical creatures escape from his case and become part of a wider conflict involving the wizarding community. Eddie Redmayne played Newt in the film.

Rowling wrote the screenplay for the film, making it her first produced screenwriting credit connected with the wizarding world. The film began a planned series that later included The Crimes of Grindelwald and The Secrets of Dumbledore.