Luna Lovegood's Hare Patronus
Brilliant Room of Requirement
Room of Requirement, Hogwarts Castle
Luna Lovegood learned to conjure her corporeal Patronus, a Hare, during her fourth year at Hogwarts. This is often regarded as an exceptionally young age for someone to have mastered such a difficult charm. It's said that her accomplishment inspired many of her peers in Dumbledore's Army to unlock their own Patronuses.