An elective monarchy is a monarchy whose reigning king or queen is elected in some form.

In the ancient Kingdom of Rome, the kings were elected by the Assemblies. The Holy Roman Empire was another historical example of this, in which the Emperor was elected by a small council of nobles called prince-electors.

A system of elective monarchy existed in Anglo-Saxon England. See Witenagemot.

In Poland, after the death of the last Piast in 1370, Polish Kings were initially elected by a small council; gradually, this privilege was granted to all members of the gentry. Kings of Poland during the times of the Polish-Lithuanian Commonwealth (1569-1795) were elected by gatherings of crowds of nobles at a field in the neighbourhood of Warsaw. Every one of an estimated 500,000 nobles could potentially have participated in such elections in person. During that time the function of the king was perfomed by an interrex.

At the start of the 20th century, several monarchs of newly-independent nations were elected by parliaments. Without a well-established hereditary royal family, new nations often chose their own monarchs from among the foreign or domestic nobility, in the hope that a stable hereditary monarchy would eventually emerge from the process. The now-defunct royal families of Finland and Germany were originally appointed in this manner.

Other monarchs, such as the Shah of Iran, have been required to undergo a parliamentary vote of approval before being allowed to ascend to the throne.

In Malaysia, the Yang di-Pertuan Agong is selected to a 5-year term from a small group of local hereditary rulers using a system of rotation, originally based on seniority, and varied by a council.

Currently, the world's only truly "elective monarchies" are Vatican City, where the Pope is elected to a life term by (and usually from) the College of Cardinals, and the Kingdom of Cambodia, in which kings are chosen for a life term by The Royal Council of the Throne from candidates of royal blood. Some may argue that the remaining communist regimes are also "elective monarchies", as successors are often chosen within the communist party. In North Korea, Kim Jong Il succeeded his father Kim Il Sung as leader. These regimes, though they possess many features of absolutism, are not officially proclaimed as monarchies.