The first name of the author who wrote the Harry Potter novels is Joanne.
J. K. Rowling was born Joanne Rowling on 31 July 1965 in Yate, Gloucestershire, England. The initial “K” was added for her publishing name because her publishers wanted a name that might appeal broadly to readers; it refers to Kathleen, her paternal grandmother, although Kathleen was not Rowling’s original middle name.
Rowling has generally been known publicly as J. K. Rowling rather than by her first name. She also published crime novels under the pseudonym Robert Galbraith, beginning with The Cuckoo’s Calling in 2013. That pen name is separate from her Harry Potter author identity.
A common mix-up is assuming that the “K” in J. K. Rowling is part of her birth name. It was adopted for publication, while Joanne is her given name.