The Metropolitan Police Service (MPS), formerly and still commonly known as the Metropolitan Police (and informally as the Met Police, the Met, Scotland Yard, or the Yard), is the territorial police force responsible for the prevention of crime and law enforcement in Greater London. In addition, the Met Police is also responsible for some specialised matters throughout the United Kingdom; these responsibilities include co-ordinating and leading national counter-terrorism measures and the personal safety of specific individuals, such as the Monarch and other members of the Royal Family, members of the Government, and other officials (such as the Leader of the Opposition).

The main geographical area of responsibilities of the Metropolitan Police District consists of the 32 London boroughs, but does not include the City of London proper – that is, the central financial district also known as the "Square Mile" – which is policed by a separate force, the City of London Police. As the force responsible for a police area that is also the capital of the United Kingdom, the Met has significant unique responsibilities and challenges, such as protecting 164 foreign embassies and High Commissions, policing London City and Heathrow Airports, policing and protecting the Palace of Westminster, and dealing with significantly more protests and events than any other force in the country, with 3,500 such events in 2016.The force, by officer numbers, is the largest in the United Kingdom by a significant margin, and one of the biggest in the world. Leaving its national responsibilities aside, the Met has the eighth-smallest police area (primary geographic area of responsibility) of the territorial police forces in the United Kingdom.

The force is led by the Commissioner, whose formal title is the Commissioner of Police of the Metropolis. The Commissioner is answerable, responsible and accountable to The Queen, the Home Office and the Mayor of London, through the Mayor's Office for Policing and Crime. The post of Commissioner was first held jointly by Sir Charles Rowan and Sir Richard Mayne. Dame Cressida Dick was Commissioner from April 2017, until her resignation in February 2022.A number of informal names and abbreviations are applied to the Metropolitan Police Service, the most common being "The Met". In colloquial London (or Cockney) slang, it is sometimes referred to as the "Old Bill". The Met is also referred to as Scotland Yard after the location of its original headquarters in a road called Great Scotland Yard in Whitehall. The Met's current headquarters is New Scotland Yard, situated on the Victoria Embankment.