Charterhouse Square is a garden square, a pentagonal space, in Farringdon, in the London Borough of Islington, and close to the former Smithfield Meat Market. The square is the largest courtyard or yard associated with the London Charterhouse, mostly formed of Tudor and Stuart architecture restored after the London Blitz. The square adjoins other buildings including a small school. It lies between Charterhouse Street, Carthusian Street and the main Charterhouse complex of buildings south of Clerkenwell Road. The complex includes a Chapel, Tudor Great Hall, Great Chamber, the Barts and The London School of Medicine and Dentistry and a 40-resident almshouse.
The 2-acre (0.8 ha) square roughly covers a large 14th-century plague pit, discovered by deep excavations for Crossrail near which, within the main site, the history of the Charterhouse is exhibited in a branch of the Museum of London. The southern end of the square forms the southern boundary of the London Borough of Islington, where it meets the City of London.