On Fairy-Stories is the Tolkien essay that explores the literary value of fairy-stories and the idea of secondary worlds.
Tolkien first delivered the work as the Andrew Lang lecture at the University of St Andrews in 1938, and it was later published in expanded form. The essay argues that fairy-stories are not only children’s entertainment. Tolkien discusses fantasy, recovery, escape and consolation, and explains how a storyteller can create a coherent secondary world.
The essay is often read as a key statement of Tolkien’s theory of fantasy. It is also connected with his broader scholarly interest in language, myth and medieval literature. “On Fairy-Stories” is sometimes confused with his Beowulf lecture, but the two works address different subjects: one develops a theory of fairy-stories, while the other analyzes Beowulf criticism.