Regicide, a person who kills a king. The most famous English regicides were the men who in 1649, under the leadership of Oliver Cromwell, tried King Charles I of England and sentenced him to death. They were members of a high court appointed by the House of Commons. Of 135 men named to the court, 67 sat in trial, and only 59 signed the death warrant.

After the monarchy was restored in 1660, many of the regicides were tried on charges of high treason. Thirteen were put to death and a number of others were imprisoned. The bodies of three deceased regicides, including Cromwell's,were dug up and hanged at Tyburn, then reburied at the foot of the scaffold.

Members of the revolutionary convention who voted the death of Louis XVI of France in 1793 were also called regicides.