A lion (Panthera leo) is a carnivorous mammal. It is the second-largest living cat after the tiger. It is the mascot of Gryffindor House at Hogwarts School of Witchcraft and Wizardry as it represents courage and chivalry, the two most pronounced traits of a Gryffindor. In addition, Luna Lovegood made a hat in the shape of a lion's head, and would wear it at all Quidditch games between Gryffindor and Slytherin Houses, to show her support for Gryffindor, over Slytherin.
It is a possible corporeal form of the Patronus Charm.