Claremont Square is a square in the Angel (Pentonville) part of Islington, London. Its central green mound, hiding a reservoir, is dotted with mature trees on all four sides (embankments). On its north side is Pentonville Road.^{[lower-alpha 1]} It is lined on the south, east and west sides by early-nineteenth-century houses, and on the north side, across the arterial road, by heavily recessed apartment/office buildings. Many of the houses have been internally subdivided.

The New River Company constructed a forerunner to today's covered reservoir, Upper Pond, in 1709. Water was pumped up to the Upper Pond from New River Head. In 1855, the Upper Pond was drained, deepened and lined with tall walls, all buffered by tree-lined embankments. The natural views and much-buried walls of the structure mean it was Grade II listed in 2000.^{[lower-alpha 2][1]} It is in use as part of London's inner Ring Main. Thames Water have exclusive access and take charge of repairs, cutting and planting, assisted by volunteer projects and residents' information. The street-side railings have a mixed set of pointed finials and form a neat, paradigmal archetype so are listed.^[2][3]

South of the main road the opening (between sides) in total measures 2.52 acres (1.02 ha), of which 1.72 acres (0.70 ha) is the green area with its directly adjoining thin pavements. Well off the south-east corner lay the former stables and stablemen's families homes (mews) which, demolished to become a close, on land taken from gardens, have been turned into a green circus (garden square) with 48 purpose-built flats.

The buildings that line all but the north side were built from 1815 to 1828. Much repaired, they have ornate brick dressings to windows and dividing storeys, with some use of white stucco and cornices, with original street-side railings. They form No.s 2 to 44 – listed grade II.^[4]

• 4 Claremont Square.
  • 1792-1834: Edward Irving, preacher.
• 21 Claremont Square
  • 18?-1882: Robert Kemp Philp, Chartist and editor
• 34 Claremont Square
  • 193? -196?: Margery Moore, musician, composer and teacher.
  • 1960s: B. S. Johnson, writer.^[5]

The Harry Potter film series uses the square as 12 Grimmauld Place.^[6] The Square is also the filming location for 35 Portland Row in the Netflix adaption of Lockwood & Co.^[7]

• British Listed Buildings Entry for Claremont Square
• Detailed description of the square with old photographs and drawings
• http://www.londongardenstrust.org/guides/site.php?tour=Islington&stage=15.00
• https://lightscameraislington.com/2013/12/12/claremont-square-harry-potter-caught-outside-number-12-grimmauld-place/