The Metropolitan Police Service (MPS), commonly known as the Metropolitan Police, and simply known as the Met Police or the "Met", is the territorial police force responsible for law enforcement and crime prevention within Greater London. In addition, it is responsible for specialised tasks throughout the United Kingdom, such as dealing with counter-terrorism throughout the UK, and the protection of certain individuals, including the monarch, royal family, governmental officials, and other designated figures. It is also referred to as an eponym as "Scotland Yard" or "the Yard", after the location of its original headquarters in Great Scotland Yard, Whitehall, in the 19th century. The Met is presently headquartered at New Scotland Yard, on the Victoria Embankment.

The main geographical area covered by the Met, the Metropolitan Police District, consists of the 32 London boroughs, and excludes the square mile of the City of London – a largely non-residential and financial district, overseen by the City of London Police. As the force responsible for the majority of the UK's capital, the Met has significant responsibilities and unique challenges, such as protecting 164 foreign embassies and High Commissions, policing London City and Heathrow airports, protecting the Palace of Westminster, and managing a higher volume of protests and events than any other British police force, with 3,500 such events in 2016.

The force, by officer numbers, ranks as the largest police force within the United Kingdom. Excluding its national roles, the Met oversees the eighth-smallest primary geographic area (police area) compared to other territorial police forces in the UK.

The force operates under the leadership of the Commissioner of Police of the Metropolis, directly accountable to the mayor of London, through the Mayor's Office for Policing and Crime and the Home Office. The post of commissioner was first held jointly by Sir Charles Rowan and Sir Richard Mayne, with Sir Mark Rowley currently holding the position since July 2022.

The Metropolitan Police Service was founded in 1829 by Home Secretary Sir Robert Peel under the Metropolitan Police Act 1829 and on 29 September of that year, the first constables of the service appeared on the streets of London. Ten years later, Metropolitan Police Act 1839 consolidated policing within London by expanding the Metropolitan Police District and either abolishing or amalgamating the various other law enforcement entities within London into the Metropolitan Police such as the Thames River Police and the Bow Street Runners.

Since January 2012, the Mayor of London is responsible for the governance of the Metropolitan Police through the Mayor's Office for Policing and Crime (MOPAC). The mayor is able to appoint someone to act on his behalf. As of November 2024^[update], the office-holder is the deputy mayor for policing and crime, Kaya Comer-Schwartz. The work of MOPAC is scrutinised by the Police and Crime Committee (also known as a police and crime panel) of the London Assembly. These structures were created by the Police Reform and Social Responsibility Act 2011 and replaced the Metropolitan Police Authority-appointed board created in 2000 by Greater London Authority Act 1999.

Before 2000, the Metropolitan Police was under the authority of the Home Secretary, the only British territorial police force to be administered by central government. The Metropolitan Police Office (MPO), although based at Scotland Yard, was a department of the Home Office created in 1829 and was responsible for the force's day-to-day administration. Under the authority of the receiver, a civilian official who was equivalent in rank to the deputy commissioner and served as the force's chief financial officer, it was headed by a civilian secretary, who was equivalent in rank to the assistant commissioners.

The area policed by the Metropolitan Police Service is known as the Metropolitan Police District (MPD). The Met was divided into 32 Borough Operational Command Units that directly aligned with the 32 London boroughs covered. This situation has changed since 2017, as the Met has attempted to save money due to cuts in funding. The MPD is now divided into 12 Basic Command Units (BCUs) made up of two, three or four boroughs. There is criticism of these changes. The City of London (which is not a London borough) is a separate police area and is the responsibility of the separate City of London Police.