The lion is the second-largest big cat, after the tiger, and is often known as the ‘king of the beasts.’ The lion is the mascot of Gryffindor House and forms part of the Hogwarts crest.
For Christmas during Harry's third year, Mrs. Weasley gave Harry a scarlet sweater decorated with a Gryffindor lion (PA11).
Gryffindor prefects' badges have a "P" in front of an image of a lion (OP9).
Luna Lovegood made a hat in the shape of a life size lion's head that roared to show support for Gryffindor at Quidditch matches. (OP19)
People of exceptional courage and bravery are said to be 'lionhearted' which makes the lion the perfect choice of animal to represent Gryffindor House.