Louise Perkins Fitzhugh was an American writer and illustrator of children's books. Fitzhugh is best known for her 1964 novel Harriet the Spy, a fiction work about an adolescent girl's predisposition with a journal covering the foibles of her friends, her classmates, and the strangers she is captivated by. The novel was later adapted into a live action film in 1996. The sequel novel, The Long Secret, was published in 1965, and its follow-up book, Sport, was published posthumously in 1979. Fitzhugh also wrote Nobody's Family Is Going to Change, which was later adapted into a short film and a play.

Harriet the Spy is a children's novel written and illustrated by Louise Fitzhugh that was published in 1964. It has been called "a milestone in children's literature" and a "classic". In the U.S., it ranked number 12 in the 50 Best Books for Kids and number 17 in the Top 100 Children's Novels on two lists generated in 2012.