Squares have long been a feature of London and come in numerous identifiable forms. The landscaping spectrum of squares stretches from those with more hardscape, constituting town squares (also known as city squares)—to those with communal gardens, for which London is a major international exponent, known as garden squares.

A few in the capital of the United Kingdom, such as Trafalgar Square, began as public open spaces in the same way as other city squares worldwide, typically a plaza, piazza and a platz in Spain, Italy and Germany. Most, however, began as garden squares i.e. private communal gardens for the inhabitants of surrounding houses. All types of the space are more prevalent in parts of London with high (urban) density. Some of these gardens are now open to the public, while others, for example around Notting Hill, are railed (a form of fencing) and private.

The terminology has been loosely applied for over a century. Some "squares" are irregularly shaped—including five triangles, a pentagon, hexagon, octagon, and two ovals among those officially named Square. Approbative and technical studies of garden squares commonly cover equivalent landscaped communal gardens not named as a Square many of which have become small public parks. A diversity of descriptive names features in the list of London's "garden squares".

"Square" is a generic term for neat, planned or set aside urban open spaces larger than a verge or pavement overlooked by buildings. In London, elements of fields were set aside, a fact reflected in the name of the square London Fields and two later examples: Coram's Fields and Lincoln's Inn Fields. Some are not actually square, or even rectangular. One reason for this is the use of a local nickname for the street, park or garden in question. Another is that some older squares were irregularly shaped to begin with, or lost their original layout due to the city's many transformations, not least following the Great Fire of London and The Blitz.

The street naming (or streetnaming) authority of each London Borough and the City of London Corporation by authority of an Act of 1939 imposes rules to authorise appropriate street names for new developments and for owners wishing to rename features.^[1] Commercial building and retained historic names apart, new residential squares must in many boroughs be "for a square only" — considered not well elongated but rectangular and to some extent open.^[2] Billiter Square, EC3 and Millennium Square, SE1 in districts dominated by retail, commerce and offices are among many modern buildings (not beside a visible rectangular open space) that include alternative, higher built density, square features to their design—such as a courtyard or a square footprint.

Some squares such as Granary Square are paved; others like Russell Square have grass and trees; many others have diverse communal gardens. Most of those that are actually square have the word in their name, and these are listed below. Others more flexibly identified do not. Such notable lists are commonly identified as list of garden squares or estate gardens, communal gardens, formal gardens, about which many books have been written. Increasingly, spaces are being constructed that are legally private, though in practice open to the public (Paternoster Square).

The Royal Borough of Kensington and Chelsea contains over a hundred garden squares whose use is restricted to residents, almost all share a name with their directly adjoining road. Residents may contract with private contractors or with the council, in which case the council charges those residents, typically at the same time as council tax.^[3] One instance is a lens (pointed oval), The Boltons.

Toward the public end of the public/private continuum, London's growth has taken in village greens. A minority of these partly or wholly survive such as Newington Green to form council-run open spaces breaking up housing, road networks and/or retail streets. The categories of greens and garden squares become more well-visited where larger than an informal scale. These are mainly government-run, characteristic parks and open spaces in London. By subtle distinction their less urban equivalent amounts to London's 26 commons most of which were diminished in the period of legal inclosure and/or the city/county's 16 country parks.

• Arundel Gardens
• Bedford Square
• Belgrave Square
• Berkeley Square
• Clapton Square
• Egerton Gardens
• Finsbury Circus
• Golden Square
• Grosvenor Square
• Hans Place
• Harrington Gardens
• Kensington Square
• Kensington Park Gardens
• Lennox Gardens, London
• Park Crescent
• Royal Crescent
• Russell Square
• St George's Square
• St. James's Square
• Sloane Square
• Soho Square
• The Boltons
• Wilton Crescent

• Trafalgar Square
• Leicester Square
• Parliament Square

This list comprises places bearing the word Square. The tables state if each has an open-air space exceeding a double-size pavement or the provision of parking spaces. Those marked mainly (due to a building, typically a church, school or community hall in the space) or yes have a clear, open space. Those marked No include streets of any shape including those with vestigial names (throwbacks) to open spaces that lay there (or adjacent) before.

Demolished squares are listed in a table at the end of this section.

Approximate area, in square metres, includes hardscapes and roads.

London's squares are arranged by postcode, see the map below of postcodes.

• List of garden squares in London
• Parks and open spaces in London