Cassia Joy Cowley, DCNZM, OBE (née Summers, born 7 August 1936, Levin, New Zealand), best known as Joy Cowley, is a New Zealand author of children's fiction, novels, and short stories.Her first novel, Nest in a Fallen Tree (1967), was adapted into the 1971 film The Night Digger by screenwriter Roald Dahl.