J.K. Rowling’s full first name is Joanne.
She was born Joanne Rowling on 31 July 1965 in Yate, Gloucestershire, England. The initials in her author name do not represent two given names: her publisher wanted a name that might appeal broadly to young readers, and Rowling used “J.K.” instead.
The “K” stands for Kathleen, her paternal grandmother’s name. Rowling did not originally have a middle name, so Kathleen was added when she adopted the pen name J.K. Rowling before the publication of Harry Potter and the Philosopher’s Stone.
Readers sometimes assume that “J.K.” is short for two given names Rowling received at birth. It is instead a publishing name built from her first name and a family name. Her later crime novels were published under the separate pseudonym Robert Galbraith.