What middle name does J.K. Rowling use professionally?

J.K. Rowling uses Kathleen as her professional middle name.

Rowling was born Joanne Rowling and did not originally have a middle name. For publication, Bloomsbury requested that she use initials rather than her full name, partly because the publisher expected boys to be reluctant to read a book by a woman. Rowling selected “K” in honor of her paternal grandmother, Kathleen.

The name appears in her author identity as J.K. Rowling, although she is commonly called Rowling or Joanne Rowling in biographical contexts. The initials are not an abbreviation of a middle name she had at birth.

The author later used different names for other kinds of writing. Her crime novels were published under the pseudonym Robert Galbraith, while her Harry Potter novels retained the J.K. Rowling name. These identities are associated with the same author but are not interchangeable credits.