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".