A garden square is a type of communal garden in an urban area wholly or substantially surrounded by buildings; commonly, it continues to be applied to public and private parks formed after such a garden becomes accessible to the public at large.

The archetypal garden square is surrounded by tall terraced houses and other types of townhouse. Because it is designed for the amenity of surrounding residents, it is subtly distinguished from a town square designed to be a public gathering place: due to its inherent private history, it may have a pattern of dedicated footpaths and tends to have considerably more plants than hard surfaces or large monuments.

At their conception in the early 17th century, each such garden was a private communal amenity for the residents of the overlooking houses akin to a garden courtyard within a palace or community. Such community courtyards date back to at least Ur in 2000 BC where two-storey houses were built of fired brick around an open square. Kitchen, working, and public spaces were located on the ground floor, with private rooms located upstairs.

In the 20th century, many garden squares that were previously accessible only to defined residents became accessible to the public. Those in central urban locations, such as Leicester Square in London's West End, have become indistinguishable from town squares. Others, while publicly accessible, are largely used by local residents and retain the character of garden squares or small communal parks. Many private squares, even in busy locations, remain private, such as Portman Square in Marylebone in London, despite its proximity to London's busiest shopping districts.

London is famous for garden squares; they are described as one of the glories of the capital. Many were built or rebuilt during the late eighteenth and early nineteenth centuries, at the height of Georgian architecture, and are surrounded by townhouses. In 1913, The UK Parliament passed the 1913 London Squares Preservation Act. The act provided enhanced legal protection to garden squares and other public spaces, ensuring they were preserved against inappropriate development and remained accessible for community enjoyment.

Large projects, such as the Bedford Estate, included garden squares in their development. The Notting Hill and Bloomsbury neighbourhoods both have many garden squares, with the former mostly still restricted to residents, and the latter open to all. Other UK cities prominent in the Georgian era such as Edinburgh, Bath, Bristol and Leeds have several garden squares.

Householders with access to a private garden square are commonly required to pay a maintenance levy. Normally the charge is set annually by a garden committee. Sometimes private garden squares are opened to the public, such as during Open Garden Squares Weekend.

Privately owned squares which survived the decades after the French Revolution and 19th century Haussmann's renovation of Paris include the Place des Vosges and Square des Épinettes in Paris. The Place des Vosges was a fashionable and expensive square to live in during the 17th and 18th centuries, and one of the central reasons that Le Marais district became so fashionable for French nobility. It was inaugurated in 1612 with a grand carrousel to celebrate the engagement of Louis XIII to Anne of Austria and is a prototype of the residential squares of European cities that were to come. What was new about the Place Royale as it was known in 1612 was that the house fronts were all built to the same design, probably by Baptiste du Cerceau.