J.K. Rowling’s first name is Joanne, represented by the initial “J” in her pen name.
She was born Joanne Rowling in 1965. The “K” was added by her publisher before the publication of Harry Potter and the Philosopher’s Stone because a name with two initials was thought to appeal to a broad readership. The K stands for Kathleen, her paternal grandmother’s name, although Kathleen was not Rowling’s original first name.
Rowling has explained that she did not have a middle name at birth. Her published name therefore combines her first name’s initial with a family name chosen as a second initial. She generally uses “J.K. Rowling” professionally, while “Joanne” remains her legal first name.
The name is sometimes incorrectly expanded as “Jane Kathleen Rowling” or another invented combination. Those versions are not correct: the initials are J for Joanne and K for Kathleen, while Rowling is her surname.