St. Mungo's Hospital for Magical Maladies and Injuries is the primary, and likely only, wizarding hospital in Great Britain. It was founded in the 1600s by the famous Healer Mungo Bonham, whose portrait hangs in the hospital. The hospital's emblem is a crossed wand and bone. To maintain secrecy from Muggles, the hospital is concealed behind the facade of a shabby-looking, red-brick department store in London called Purge and Dowse, Ltd.. The exterior is deliberately uninviting, with dusty windows displaying broken mannequins in outdated fashions. Entry is gained by approaching a specific female mannequin in the window and speaking to it. The visitor then simply walks through the display glass, which ripples like water, to arrive in the hospital's reception area. The reception is a crowded and chaotic hall, often filled with witches and wizards suffering from various comical or serious magical afflictions. A Welcome Witch sits at an enquiry desk to direct patients and visitors. The atmosphere is frantic, with sounds of screams, bangs, and strange magical occurrences. The walls are lined with portraits of notable Healers, including one of Urquhart Rackharrow, the inventor of the Entrail-expelling Curse.
St. Mungo's is a key location in Harry Potter and the Order of the Phoenix. Following his attack by Nagini in the Department of Mysteries, Arthur Weasley is brought to St. Mungo's for treatment. Harry Potter and the Weasley family visit him on Christmas Day, providing Harry with his first detailed look inside the wizarding world's primary medical institution. During these visits, the group overhears conversations about Broderick Bode's mysterious strangulation by a potted Devil's Snare, hinting at the Death Eaters' attempts to retrieve the prophecy. Most significantly, it is here that Harry, Ron Weasley, Hermione Granger, and Ginny Weasley encounter Neville Longbottom visiting his parents, Frank Longbottom and Alice Longbottom. They are permanent residents of the Janus Thickey Ward for long-term spell damage, having been tortured into insanity by Bellatrix Lestrange and other Death Eaters. This encounter is a pivotal moment for understanding Neville's character and the true cost of the First Wizarding War. The group also finds their former Defence Against the Dark Arts professor, Gilderoy Lockhart, in the same ward, still suffering from amnesia caused by a backfired Memory Charm. The hospital is mentioned on other occasions:
St. Mungo's is organized by floor, with each floor dedicated to a specific category of magical malady.