Manchester Square is an 18th-century garden square in Marylebone, London. Centred 950 feet (290 m) north of Oxford Street it measures 300 feet (91 m) internally north-to-south, and 280 feet (85 m) across. It is a small Georgian predominantly 1770s-designed instance in central London; construction began around 1776. The north side has a central mansion, Hertford House, flanked by approach ways; its first name was Manchester House — its use is since 1897 as the Wallace Collection (gallery/museum) of fine and decorative arts sits alongside the Madame Tussauds museum and the Wigmore Hall concert rooms. The square forms part of west Marylebone, most of which sees minor but overarching property interests held by one owner among which many buildings have been recognised by statutory protection.

The Portman Estate, covering 110 acres of Marylebone in London’s West End, was founded in 1532 when the land was first leased to Sir William Portman.