The Metropolitan Police District (MPD) is the police area which is policed by the Metropolitan Police Service in London. It currently consists of the ceremonial county of Greater London, which excludes the City of London. The Metropolitan Police District was created by the Metropolitan Police Act 1829 as an ad hoc area of administration because the built-up area of London spread at the time into many parishes and counties without an established boundary. The district expanded as the built up area grew and stretched some distance into rural land. When county police forces were set up in England, those of Essex, Hertfordshire, Kent and Surrey did not cover the parts of the counties within the MPD, while Middlesex did not have a county force. Similarly, boroughs in the MPD that elsewhere would have been entitled to their own police force did not have them.

The Metropolitan Police Service (MPS), also officially known as the Metropolitan Police, which is still its common name, serves as the territorial police force responsible for law enforcement and crime prevention within the ceremonial county of Greater London. In addition, it is responsible for specialised tasks throughout the United Kingdom, such as UK counter-terrorism measures, and the protection of certain individuals, including the monarch, royal family, governmental officials, and other designated figures. Commonly referred to as the Met, it is also referred to as Scotland Yard or the Yard, after the location of its original headquarters in Great Scotland Yard, Whitehall in the 19th century. Its present headquarters are near there at New Scotland Yard on the Victoria Embankment.