Ann Matthews Martin (born August 12, 1955) is an American children's author.

Ann Martin grew up in Princeton, New Jersey with her parents and her younger sister, Jane. After graduating from Smith College, Martin became a teacher and then an editor of children's books; she is now a full-time writer. Martin finds the ideas for her books from many different sources; some are based on personal experiences, while others are based on childhood memories and feelings. Many are about contemporary problems or events. All of Ann's characters, including the members of The Baby-Sitters Club, are fictional, but many of her characters are based on real people. Sometimes Ann names her characters after people she knows, and other times she simply chooses names that she likes.

Martin has always enjoyed writing. Even before she was old enough to write, she would dictate stories to her mother to write down for her. Some of her favorite authors at that time were Lewis Carroll, P. L. Travers, Hugh Lofting, Astrid Lindgren, and Roald Dahl. They inspired her to become a writer herself. Since ending The Baby-Sitters Club series in 2000, Martin’s writing has concentrated on single novels, many of which are set in the 1960s. One of those novels, A Corner of the Universe, won a Newbery Honor in 2003. In 2010, Martin published a prequel to The Baby-Sitters Club series titled The Summer Before.

After living in New York City for many years, Martin moved to the Hudson Valley in upstate New York where she now lives with her dog, Sadie, and her cats, Gussie, Pippen, and Woody. Her hobbies include needlepoint, fostering cats, and gardening. Her favorite thing to do is to make clothes for children . According to the biographical blurb in the back of The Baby-Sitters Club novels, she likes ice cream, her favorite TV show is I Love Lucy, and she hates to cook. In 1990, she created the Ann M. Martin Foundation, which provides grants to causes benefiting children, education/literacy programs, and homeless people and animals.