Minerva McGonagall Minerva McGonagall is Deputy Headmistress, head of Gryffindor House, Transfiguration professor, and later Headmistress at Hogwarts, where she began teaching in December 1956. She is first introduced in the opening chapter of Harry Potter and the Philosopher's Stone, when she meets Dumbledore at Number 4 Privet Drive, Little Whinging, Surrey (the home of Harry Potter's aunt and uncle). McGonagall is described as a tall, rather severe-looking woman, with black hair typically drawn into a tight bun. She wears emerald green robes, a pointed hat, and always has a very prim expression. She is, according to Rowling, a sprightly 70-year-old.[8] McGonagall wears square spectacles that match the markings around the eyes of her Animagus form of a silver tabby cat; she has the distinction of being the first Animagus introduced in the series and being one of the few registered Animagi of the century. Harry's immediate impression of her is of someone who is not to be crossed. She has a fondness for tartan, and her handkerchief, dressing gown and dress robes are patterned with it. Rowling has said McGonagall's birthday is 4 October.[9]

In the first book, after seeing Harry fly masterfully his very first time on a broom, she recommends him to fill the position of Seeker, even though first years are normally prohibited from playing, and sends Harry a broom. Furthermore, although a strict disciplinarian, she often assists Harry indirectly with activities that are not strictly within the rules of Hogwarts; for example, she allows Harry and his friends to use the Transfiguration classroom to practice for tasks in the Triwizard Tournament. She promises Harry she would do everything in her power to help him to achieve his goal of becoming an Auror, and she keeps her promise.[10] Despite her stern front, McGonagall is shown to have good intentions at heart and has been known to display a range of emotions, which can often be a shock to her colleagues and students.

It is revealed in Order of the Phoenix that McGonagall is a member of the Order of the Phoenix. She and Dolores Umbridge seem to have a mutual dislike for each other, as Umbridge continuously usurps more and more power from the staff and from Dumbledore and McGonagall in particular. When McGonagall attempts to stop Umbridge and her fellow Ministry cronies from unjustly taking Hagrid away by force, she is hit by four Stunning Spells without warning, before she can draw her wand. The unconscious septuagenarian is rushed to St Mungo's, where she recovers for awhile. McGonagall returns to the school towards the end of the book, though she temporarily uses a walking stick to support herself. She is, however, an exceptional duellist capable of holding her own against much younger and more agile foes. During their duel she appears to be equal in strength to Snape, himself noted as an especially powerful wizard.

After the death of Dumbledore at the hands of Snape in Half-Blood Prince, she becomes the acting Headmistress of Hogwarts. However, in the series finale, she does not become headmistress at the start of term as expected; Snape is appointed by new Minister for Magic Pius Thicknesse, who is actually under the Imperius Curse and acting for Voldemort. Despite the many changes, she is retained as head of Gryffindor House. Before the Battle of Hogwarts, she goes to the Ravenclaw tower and finds Alecto Carrow stunned and her brother Amycus searching for Harry. When Amycus suggests hurting the students to compensate for his sister's state, McGonagall immediately intervenes. In response, Amycus spits in her face. Harry, who was present and hidden under his invisibility cloak, reveals himself and uses the Cruciatus Curse on Amycus. Harry then informs McGonagall that Voldemort is on his way and she sends three Patronuses — which manifest in her Animagus form — to warn the other three Heads of House.[11] When on her way to meet the Heads of House, she meets Snape, who questions her about Potter's whereabouts. Not knowing Snape is actually still following Dumbledore's orders and has important information for Harry, she attacks him, engaging in a fierce duel. With help from Professors Sprout and Flitwick, she succeeds in driving Snape away.

McGonagall then takes charge of the school again and proceeds to secure it against Voldemort to ensure Harry can fulfil his mission from Dumbledore. She also organises the evacuation of the school's under-age students to ensure their safety. She then leads the remaining students, the staff of Hogwarts, and members of the Order of the Phoenix in the fight against Voldemort. She is seen during the battle with a large gash on her cheek and commanding a herd of charmed desks to charge at Death Eaters. Finally, McGonagall ends up duelling Voldemort alongside Kingsley Shacklebolt and Horace Slughorn. As is confirmed in The Tales of Beedle the Bard, McGonagall becomes Headmistress of Hogwarts after the Battle of Hogwarts and Snape's death; however, in an interview J. K. Rowling said McGonagall would be retired by the time of the Deathly Hallows epilogue (19 years after the main events of Deathly Hallows), as she is "getting on in years."

McGonagall is played by Dame Maggie Smith in the film adaptations. Smith has described her role as "Miss Jean Brodie in a wizard's hat", Given that her role becomes progressively smaller as the series goes on, she notes that Harry Potter and the Philosopher's Stone is her favourite thus far.[12] Rowling has stated that she always pictured Smith portraying McGonagall, and claimed the actress to be in the top of her list.[13]

Rowling named the character after the poet William Topaz McGonagall whose name she liked. Her first name, Minerva, comes from the Roman goddess of wisdom. [14]