What middle name did J.K. Rowling adopt for her published name?

J.K. Rowling adopted Kathleen as the middle name in her published name.

She was born Joanne Rowling and did not originally have a middle name. When Harry Potter and the Philosopher’s Stone was prepared for publication, her publisher asked her to use two initials because they believed young boys might be less likely to choose a book written by a woman. Rowling selected K in honor of her paternal grandmother, Kathleen.

The resulting author name, J.K. Rowling, does not mean that her birth name was Joanne Kathleen Rowling. Kathleen was added for publishing purposes. Rowling has also explained that she was called Jo by family and friends, rather than Joanne in ordinary conversation.

The initials became one of the most recognizable author brands in modern publishing. After the Harry Potter series, Rowling published The Casual Vacancy under her own initials and released crime novels under the separate pseudonym Robert Galbraith.