J.K. Rowling’s full first name is Joanne Kathleen.
She was born Joanne Rowling on 31 July 1965 at Yate General Hospital near Bristol, England. The middle initial K was chosen in honor of her paternal grandmother, Kathleen, although Rowling did not originally have a middle name.
Her publisher wanted a name that might appeal broadly to young readers, so she used initials rather than her full first name. The surname Rowling is pronounced like “rolling,” and the initials are not an abbreviation for a separate pen name. Rowling later used the name Robert Galbraith for her crime novels, but that is a distinct pseudonym, not an expansion of J.K.
The name Joanne Kathleen Rowling therefore belongs to the author publicly known as J.K. Rowling, while “Jo” is a common short form used by people familiar with her.