Avon and Somerset Police is the territorial police force responsible for law enforcement in the five unitary authority areas of Bristol, Bath and North East Somerset, North Somerset, Somerset, and South Gloucestershire, all in South West England.

As of September 2020^[update], the force had 2,965 police officers, 299 special constables, and 330 police community support officers. The force serves 1.72 million people over an area of 1,847 square miles (4,780 km²).

According to a House of Commons Library report, as of March 2023, Avon and Somerset Police had 3,330 Police Constables and 235 Special Constables.

The police area covered by Avon & Somerset Police today can trace its policing heritage back to the very start of the modern policing system. The Municipal Corporations Act 1835 created municipal boroughs across England and Wales, each with the power to create a borough police force. Before then, policing was largely unrecognisable from today's system, with watchmen and parish constables providing variable levels of law enforcement, if any, driven largely by magistrates. As a result of the Act the following borough police forces were created within the current Avon and Somerset Police area: Bath City Police (1836), Bristol Constabulary (1836), Bridgwater Borough Police (1836), Wells City Police (1836), Glastonbury Borough Police, Chard Borough Police (1839), and Yeovil Borough Police (1854).

However, outside the new boroughs there was no modern police. Therefore, the government introduced the County Police Act 1839 which permitted county authorities to set up county forces to police areas outside of the boroughs. Following these Acts, Gloucestershire Constabulary was created in 1839, which covered what is now the north part of the Avon & Somerset Constabulary area (South Gloucestershire). But there was still some opposition to the new model of policing, and rural Somerset had no police force until 1856. The County and Borough Police Act 1856 mandated county authorities to set up a constabulary. Somerset Constabulary commenced policing the county in 1856, and Wells City Police and Glastonbury Borough Police were merged into the new county force almost immediately; Yeovil Borough Police followed a year later.

Later in the 19th century the Local Government Act 1888 required that all boroughs with populations of less than 10,000 amalgamate their police force with the adjoining county constabulary. This signalled the end of Chard Borough Police, which merged into Somerset Constabulary on 1 April 1888. In 1940, Bridgwater Borough Police voluntarily became part of Somerset constabulary, with the 20 officers of the borough police becoming Somerset County officers upon merger.

During the 20th century, the number of separate police forces in the United Kingdom was reduced on grounds of efficiency. The Police Act 1964 gave the Home Secretary the power to enforce amalgamations, but this was not required when Somerset Constabulary and Bath City Police voluntarily agreed to merge forming the Somerset and Bath Constabulary on 1 January 1967. This resulted in three police forces covering the current area of the Avon & Somerset Constabulary: Somerset and Bath Constabulary, Bristol Constabulary, and Gloucestershire Constabulary (in the far north). The next change was on 1 April 1974, with the implementation the Local Government Act 1972, which created Avon and Somerset Constabulary, a merger of Somerset and Bath Constabulary, Bristol Constabulary, and the southern part of Gloucestershire Constabulary.

In 2014, the force announced that in order to reduce its budget, it would close 12 local police stations as part of a planned 36% reduction of the number of buildings it occupied. Police and Crime Commissioner Sue Mountstevens said these buildings were "outdated" and "under-occupied". The stations were seven in Bristol, and those in Bath, Keynsham, Nailsea, Radstock and Weston-super-Mare.