Charterhouse Square is a historic square in Smithfield, between Charterhouse Street and Clerkenwell Road. It lies in the extreme south of the London Borough of Islington, just north of the City of London.
The Charterhouse is on the site of a former Carthusian monastery founded in 1371, by Walter de Manny, on what is now the north side of the square. It was established near a 1348 plague pit, located in the square, which formed the largest mass grave in London during the Black Death when around half the population died of the plague. Tens of thousands of bodies were buried here. The name is derived as an Anglicisation of La Grande Chartreuse, whose order founded the monastery.
The Charterhouse was dissolved as a monastery in 1537, and in 1545 was purchased by Sir Edward (later Lord) North (c. 1496-1564) and transformed into a mansion house. Following North's death, the property was bought by Thomas Howard, 4th Duke of Norfolk, who was imprisoned there in 1570 after scheming to marry Mary, Queen of Scots. Later, Thomas Sutton bought the Charterhouse, and on his death in 1611, endowed a hospital (almshouse) and school on the site, which opened in 1614, supporting eighty pensioners (known as 'brothers'). The school for boys coexisted with the home for pensioners until 1872 when Charterhouse School moved to Godalming in Surrey. Following this, the Merchant Taylors' School occupied the buildings until 1933.
Today, the Charterhouse Square campus of Queen Mary, University of London is situated to the north-east of Charterhouse Square, occupying the former school lands. This includes student accommodation and departments of Barts and The London School of Medicine and Dentistry. The City of London Migraine Clinic is situated to the South-west of Charterhouse Square.
Florin Court is a residential building in the Art Deco style on the eastern side of the square, built in 1936 by Guy Morgan and Partners. It was used as the fictional residence of Hercule Poirot, Whitehaven Mansions, in the 1980s TV series based on Agatha Christie's crime novels. The building has a curved facade, roof garden and basement swimming pool.
The independent preparatory Charterhouse Square School is on the south side of the square.
Smithfield Market is to the south-west along Charterhouse Street.
The nearest underground station is the Barbican tube station to the south-east.