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. It is a public institution dedicated to treating a wide array of magic-related ailments, from spell damage to creature-inflicted wounds. The hospital is cleverly concealed from Muggle view. Its public entrance is located in London through a seemingly abandoned, red-brick department store named Purge and Dowse, Ltd. The shop front appears grimy and its window displays feature dusty mannequins in outdated fashions. To gain entry, a witch or wizard must address a specific mannequin in the window, which will give a small nod and gesture for them to walk through the glass as if it were water. Inside, the reception area is often crowded and chaotic, filled with witches and wizards suffering from bizarre magical afflictions. A Welcome Witch sits at an enquiry desk to direct patients and visitors. The hospital is staffed by Healers, who are the magical equivalent of doctors and are distinguished by their lime-green robes.
St. Mungo's is a key location in Harry Potter and the Order of the Phoenix. After Arthur Weasley is savagely attacked by Voldemort's snake, Nagini, he is taken to St. Mungo's for urgent care. Harry Potter, Hermione Granger, and the Weasley children visit him there over Christmas, providing Harry his first look inside the wizarding world's medical center. During one of these visits, Harry, Ron Weasley, and Hermione accidentally encounter their former Defence Against the Dark Arts professor, Gilderoy Lockhart, who remains a permanent patient due to a backfired Memory Charm. More significantly, they witness Neville Longbottom visiting his parents, Frank and Alice Longbottom. They learn that Neville's parents were Aurors who were tortured into insanity with the Cruciatus Curse by Death Eaters, including Bellatrix Lestrange. This moment is a profound and sombre revelation for Harry and a crucial point of character development for Neville. Later in the same book, Minerva McGonagall is admitted to St. Mungo's to recover after being hit with four simultaneous Stunning Spells while defending Rubeus Hagrid from Dolores Umbridge and other Ministry of Magic officials. In Harry Potter and the Half-Blood Prince, Katie Bell is sent to St. Mungo's for several months of treatment after she comes into contact with a cursed opal necklace intended for Albus Dumbledore. The hospital is also mentioned as a destination for the injured following the Battle of the Astronomy Tower and the Battle of Hogwarts.
The hospital is organized into different floors, each specializing in a particular type of magical malady or injury.