Luna Lovegood's Patronus is a hare, and is first seen in Harry Potter and the Order of the Phoenix during the scene that Harry is teaching the members of Dumbledore's Army the Expecto Patronum charm.

which is why Harry Potter and Luna Lovegood (Evanna Lynch) were the only two students who could see them. Those who cast the Thestral as their Patronus charm are typically empathetic people with a ...