What is the name of J.K. Rowling’s fairy-tale collection mentioned in Harry Potter and the Deathly Hallows?

The fairy-tale collection mentioned in Harry Potter and the Deathly Hallows is The Tales of Beedle the Bard.

Within the story, Beedle’s collection is a familiar wizarding book of moral tales. Dumbledore leaves Hermione Granger his annotated copy, and its notes help the trio understand the significance of the Deathly Hallows.

The most important tale for the final novel is “The Tale of the Three Brothers.” It describes three brothers who receive powerful magical objects, including the Elder Wand, the Resurrection Stone, and the Cloak of Invisibility. The story gives the trio a clue about the origin and meaning of the Hallows.

Rowling later published The Tales of Beedle the Bard as a real book in 2008. Its publication extended a fictional textbook-like work into the real world, similar to earlier companion titles connected with Hogwarts.