A police force is a constituted body of persons empowered by a state to enforce the law, to protect people and property, and to prevent crime and civil disorder. Their powers include the power of arrest and the legitimised use of force. The term is most commonly associated with police services of a sovereign state that are authorised to exercise the police power of that state within a defined legal or territorial area of responsibility. Police forces are often defined as being separate from military or other organisations involved in the defense of the state against foreign aggressors; however, gendarmerie are military units charged with civil policing. The police force is usually a public sector service, funded through taxes.

Law enforcement is only part of policing activity. Policing has included an array of activities in different situations, but the predominant ones are concerned with the preservation of order. In some societies, in the late 18th and early 19th centuries, these developed within the context of maintaining the class system and the protection of private property. Police forces have become ubiquitous in modern societies.

In Australia the first police force having centralised command as well as jurisdiction over an entire colony was the South Australia Police, formed in 1838 under Henry Inman.

However, whilst the NSW Police Force was established in 1862, it was made up from a large number of policing and military units operating within the then Colony of New South Wales and traces its links back to the Royal Marines. The passing of the Police Regulation Act of 1862 essentially tightly regulated and centralised all of the police forces operating in the colony of NSW.

The NSW Police Force remains the largest police force in Australia in terms of personnel and physical resources. It is also the only police force that requires its recruits to undertake university studies at the recruit level and has the recruit pay for their own education.