What middle name did J.K. Rowling use in her author name?

J.K. Rowling used Kathleen as the middle name represented by the letter K.

Rowling was born Joanne Rowling, without a middle name. Before publication, Bloomsbury asked her to use two initials because the publisher believed boys might be less likely to choose a book written by a woman if the author’s full name appeared on the cover. Rowling selected “K” in honor of her paternal grandmother, Kathleen Ada Bulgen.

The name “J. K. Rowling” therefore does not record a birth middle name. Rowling has explained that she adopted the initials for professional reasons, while the added initial also created a distinctive author identity. Her legal and public naming history has sometimes caused confusion because she has also used the name Joanne Kathleen Rowling.

She later wrote the Cormoran Strike crime novels under the pseudonym Robert Galbraith.