Chief Constable is the rank used by the chief police officer of every territorial police force in the United Kingdom except for the City of London Police and the Metropolitan Police, as well as the chief officers of the three 'special' national police forces, the British Transport Police, Ministry of Defence Police, and Civil Nuclear Constabulary. The title is also held by the chief officers of the principal Crown Dependency police forces and the Sovereign Base Areas Police in Cyprus. The title was also held, ex officio, by the president of the Association of Chief Police Officers under the Police Reform Act 2002. It was also the title of the chief officer of the Royal Parks Constabulary until this agency was disbanded in 2004.

A constable is a person holding a particular office, most commonly in criminal law enforcement. The office of constable can vary significantly in different jurisdictions. A constable is commonly the rank of an officer within the police. Other people may be granted powers of a constable without holding this title.