||This article needs additional citations for
verification. (November 2014)
A usurper is an illegitimate or controversial claimant to
power, often but not always in a
monarchy. This may include a person who succeeds in establishing himself as a monarch without inheriting the throne or any other person exercising authority unconstitutionally. A person who takes the power of the
country for himself or herself at the expense of the
people. It may also be applied to an official acting
ultra vires, outside his authority or jurisdiction.