Lord Protector (pl. Lords Protectors) is a title used in British constitutional law for certain heads of state at different periods of history. It is also a particular title for the British Heads of State in respect to the established church. It is sometimes used to render in English other posts of temporary regent, acting for the absent monarchic head of state.

The title of THE Lord Protector was originally used by royal princes or other nobles exercising an individual regency (i.e., not merely member of a collegial regency council) while the English monarch was still a minor or otherwise unable to rule.

Notable cases in England are:

Cases in Scotland:

The Lord Protector of the Commonwealth of England, Scotland and Ireland was the title of the head of state during the Interregnum, following the first period of the Commonwealth under Council of State government. It was held by Oliver Cromwell (December 1653–September 1658) and his son and designated successor Richard Cromwell (September 1658–May 1659) during what is now known as The Protectorate.