Chief police officer is a phrase used in the United Kingdom to describe the position held by the most senior police officer in a police force. It refers to either one of the 53 Chief Constables, the Commissioner of the City of London Police or the Commissioner of the Metropolitan Police. Such police officers are members of the Association of Chief Police Officers. The phrase is used in legislation when giving powers such as those to permit public processions, or grant firearms licenses. Some such activities can usually be delegated to any constable.

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, the Isle of Man Constabulary, States of Guernsey Police Service, and States of Jersey Police. The title is 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.