Minerva McGonagall is a fictional character in the "Harry Potter" books written by J. K. Rowling. This character is a teacher at the school Hogwarts, and a good character in the series. She helps Harry Potter, the main character, many times in the series. She teaches "transfiguration", a type of magic where you change objects or animals into other objects and animals. At the end of the books, McGonagall becomes the school principal. Her honorary title is Hogwarts Headmistress.