Susan Mary Cooper is an English author of children's books, born on 23 May 1935. She is best known for her series The Dark Is Rising, a contemporary fantasy series set in England and Wales that incorporates British mythology such as the Arthurian legends and Welsh folk heroes.

In 2012, she won the lifetime Margaret A. Edwards Award from the American Library Association, recognizing her contribution to writing for teens. During the 1970s, two of the five novels were named the year's best English-language book with an "authentic Welsh background" by the Welsh Books Council. In 2024, the Science Fiction and Fantasy Writers Association named her the 40th Damon Knight Memorial Grand Master in recognition of her significant contributions to the literature of science fiction and fantasy.