What 1939 lecture by J.R.R. Tolkien became a major essay about fantasy and fairy stories?

J.R.R. Tolkien’s 1939 lecture about fantasy and fairy stories became the essay On Fairy-Stories.

Tolkien delivered the lecture as the Andrew Lang lecture at the University of St Andrews in Scotland on 8 March 1939. The essay was later published in expanded form and became one of his most influential statements about imaginative literature.

In it, Tolkien discusses what he calls the fairy-story, arguing that such stories are not merely childish tales. He examines fantasy, recovery, escape, and consolation, and describes the “eucatastrophe,” a sudden turn from apparent disaster to joy.

The essay is often read alongside Tolkien’s fiction because it explains principles visible in The Hobbit and The Lord of the Rings. It does not present a simple definition of all fantasy, but it gives Tolkien’s own account of why invented worlds and old tales can have serious artistic and emotional value.