The Metropolitan Special Constabulary (MSC) is the volunteer police force of the Metropolitan Police Service. It is one of three Special Constabularies operating within London, the others being part of the City of London Police and British Transport Police. The service was created over 190 years ago under the Special Constables Act 1831. As of November 2021^[update] it consists of 1,450 officers, making it the largest in the UK.

Special Constables are warranted Police Officers who hold the Office of Constable and have the same powers and privileges of a regular Police Officer throughout England and Wales and are subject to the same standards of professional behaviour as any Police Officer would under The Police (Conduct) Regulations 2012. They wear the same uniform and engage in the same work as regular Police Officers, including foot and vehicle patrols (whether alone, with another Special Constable or with a regular Police Officer), attending incidents, specific operations and the policing of major events.

Special Constables are required to undertake a minimum of 200 hours of operational duties every year, spread over a minimum of 16 hours per month. However, many do more than the basic requirement.

Each Basic Command Unit (BCU) that provides policing for 2-4 London boroughs has a contingent of Special Constables supervised by a number of Special Sergeants, Special Inspectors and a Special Chief Inspector, who work in partnership with a number of regular officers. Most Command Units have more than 100 MSC officers and Westminster, the biggest, has over 300.

Several Special Constables are sponsored by their employers' as part of the Employer Supported Policing (ESP) programme, in which employers release their employees for a specific amount of time frequently to perform policing duties.

Special Constables have the freedom, to some degree, in the choice of Borough they work in, their duties and hours. The teams in which Specials work depends on their BCU - some choosing to task their Specials to Safer Neighbourhoods Teams (known in other constabularies as Neighbourhood Policing Teams), others to their Emergency Response and Patrol Teams (known colloquially as Response Teams), whilst others work on a variety of other local portfolios such as the Criminal Investigation Department, Safeguarding or with schools. Additionally, there are Special Constables who work for more specialist and non-local policing units such as the Marine Policing Unit, Heathrow Airport OCU (ID), Organised Crime, Roads & Transport Policing Command.

Special Constables undergo a structured recruitment process from application to the offer of an appointment. After an initial assessment of a Specials application, suitable candidates are invited to attend the Selection Centre, held at Empress State Building or another Met site.

In 2014 the assessment process was combined into a single day (compared to the separate Day One, Day Two process). The one-day event allows the timely release of candidates that have failed any of the assessments. Throughout the day, the following qualities and competencies are assessed: decision making, communication, personal responsibility, resilience, respect for diversity, customer focus and teamwork.