Under what pen name did J.K. Rowling publish the first Cormoran Strike novel?

J.K. Rowling published the first Cormoran Strike novel under the pen name Robert Galbraith.

The novel, The Cuckoo's Calling, appeared in April 2013 and introduced private detective Cormoran Strike and his assistant Robin Ellacott. Rowling later confirmed that Robert Galbraith was a pseudonym she had chosen for the crime-fiction series.

The name was not intended to identify another real author. Rowling said the pseudonym gave her a different publishing identity and allowed her to receive feedback without the expectations attached to Harry Potter. The series continued with novels including The Silkworm, Career of Evil, Lethal White, Troubled Blood, The Ink Black Heart, and The Running Grave.