Kay O'Neill (also known as Katie O'Neill and K. O'Neill) is an illustrator and writer from New Zealand.
O'Neill is a self-taught artist who has produced several comics and graphic novels. They initially built a fan base by publishing comics on their Tumblr page, such as Princess Princess, which was later published as a book by Oni Press as Princess Princess Ever After. O'Neill notes "a different kind of accessibility and visibility that comes with a book, particularly one that is in easy reach of kids’ hands in school and public libraries".
Their graphic novels cover fantasy, slice-of-life stories which are intended for all ages. These have won multiple awards, with The Tea Dragon Society in particular winning two Eisner Awards, a Harvey Award, and a Dwayne McDuffie Award for Kids' Comics. The Tea Dragon Society also led to a card game and plushies, and another Tea Dragon book was published in 2019. When not working on a book, O'Neill is a fulltime freelance illustrator.