Lord Protector

 was a title of a ruler of a country ordinarily ruled by a king or a queen. During this time, the country would be referred to as a Protectorate rather than a Kingdom.

In the 1650s, first Oliver Cromwell and, after his death in 1658, his son, Richard Cromwell held the title of the Lord Protector of England, Scotland and Ireland. (PROSE: The Roundheads)