What pen name did Joanne Rowling use for the Harry Potter books?

Joanne Rowling used the pen name J.K. Rowling for the Harry Potter books.

Rowling’s publisher suggested using two initials rather than her full first name because the market research of the time indicated that some boys might be less likely to choose a book written by a woman. Rowling had no middle name, so she adopted Kathleen, her paternal grandmother’s name, as the K in the author name.

The first Harry Potter novel was published as by J.K. Rowling in 1997. The name became globally associated with the series, although Rowling has continued to be identified in biographies by her given name, Joanne Rowling.

In 2013, she also began publishing crime novels under the pseudonym Robert Galbraith. That name was separate from J.K. Rowling and was used for the Cormoran Strike series. The two pseudonyms are therefore not interchangeable: J.K. Rowling is the name attached to Harry Potter, while Robert Galbraith is the original name used for her crime fiction.