There are 43 sovereign states in the world with a monarch as Head of state. They fall roughly into the following categories:
- Commonwealth realms. Queen Elizabeth II is the monarch of sixteen Commonwealth realms (Antigua and Barbuda, the Commonwealth of Australia, the Commonwealth of the Bahamas, Barbados, Belize, Canada, Grenada, Jamaica, New Zealand, the Independent State of Papua New Guinea, the Federation of Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines, Solomon Islands, Tuvalu and the United Kingdom of Great Britain and Northern Ireland). They have evolved out of the British Empire into fully independent states within the Commonwealth of Nations that retain the Queen as head of state, unlike other Commonwealth countries that are either dependencies, republics or have a different royal house. All sixteen realms are constitutional monarchies and full democracies where the Queen has limited powers or a largely ceremonial role. The Queen is head of the established Protestant Christian Church of England in the United Kingdom, while the other 15 realms do not have an established church.
- Other European constitutional monarchies.
- The Principality of Andorra, the Kingdom of Belgium, the Kingdom of Denmark, the Grand Duchy of Luxembourg, the Kingdom of the Netherlands, the Kingdom of Norway, the Kingdom of Spain, and the Kingdom of Sweden are fully democratic states in which the monarch has a limited or largely ceremonial role.
- There is generally a Christian religion established as the official church in each of these countries. This is the Lutheran form of Protestantism in Norway, Sweden and Denmark, while Belgium and Andorra are Roman Catholic countries. Spain and the Netherlands have no official state religion. Luxembourg, which is very predominantly Roman Catholic, has five so-called officially recognized cults of national importance (Roman Catholicism, Protestantism, Greek Orthodoxy, Judaism and Islam), a status which gives to those religions some privileges like the payment of a state salary to their priests.
- Andorra is unique among all existing monarchies, as it is, by definition, a diarchy, with the Co-Princeship being shared by the President of France and the Bishop of Urgell. This situation, based on historic precedence, has created a peculiar situation among monarchies, as a) both Co-Princes are not of Andorran descent, b) one is elected by common citizens of a foreign country (France), but not by Andorrans as they cannot vote in the French Presidential Elections, c) the other, the bishop of Urgel, is appointed by a foreign head of state, the Pope.
- European constitutional/absolute monarchies. Liechtenstein and Monaco are constitutional monarchies in which the Prince retains many powers of an absolute monarch. For example, the 2003 Constitution referendum which gives the Prince of Liechtenstein the power to veto any law that the Landtag (parliament) proposes and the Landtag can veto any law that the Prince tries to pass. The Prince can hire or dismiss any elective member or government employee from his or her post. However, what makes him not an absolute monarch is that the people can call for a referendum to end the monarchy’s reign. The Prince of Monaco has simpler powers but cannot hire or dismiss any elective member or government employee from his or her post, but he can elect the minister of state, government council and judges. Both Albert II and Hans-Adam II have quite a bit of political power, but they also own huge tracts of land and are shareholders in many companies.
- Muslim monarchies. These Muslim monarchs of the Kingdom of Bahrain, the Nation of Brunei, the Abode of Peace, the Hashemite Kingdom of Jordan, the State of Kuwait, the Kingdom of Morocco, the Sultanate of Oman, the State of Qatar, the Kingdom of Saudi Arabia, and the United Arab Emirates generally retain far more powers than their European or Commonwealth counterparts. The same goes for Malaysia where Islam is the official religion of the federation. The Nation of Brunei, the Abode of Peace, the Sultanate of Oman, the State of Qatar, and the Kingdom of Saudi Arabia remain absolute monarchies; the Kingdom of Bahrain, the State of Kuwait and United Arab Emirates are classified as mixed, meaning there are representative bodies of some kind, but the monarch retains most of his powers. The Hashemite Kingdom of Jordan, Malaysia and the Kingdom of Morocco are constitutional monarchies, but their monarchs still retain more substantial powers than European equivalents.
- East Asian constitutional monarchies. The Kingdom of Bhutan, the Kingdom of Cambodia, Japan, the Kingdom of Thailand have constitutional monarchies where the monarch has a limited or ceremonial role. The Kingdom of Bhutan, Japan and the Kingdom of Thailand are countries that were never colonized by European powers, but Japan and the Kingdom of Thailand have changed from traditional absolute monarchies into constitutional ones during the twentieth century, while the Kingdom of Bhutan changed in 2008. The Kingdom of Cambodia had its own monarchy after independence from the French Colonial Empire, which was deposed after the Khmer Rouge came into power and the subsequent invasion by the Socialist Republic of Vietnam. The monarchy was subsequently restored in the peace agreement of 1993.
- Other monarchies. Five monarchies do not fit into one of the above groups by virtue of geography or class of monarchy: the Kingdom of Tonga in Polynesia; the Kingdom of Swaziland and the Kingdom of Lesotho in Africa; and the Sovereign Military Order of Malta and the Vatican City State in Europe. Of these, the Kingdom of Lesotho and the Kingdom of Tonga are constitutional monarchies, while the Kingdom of Swaziland and the Vatican City State are absolute monarchies. The Kingdom of Swaziland is also unique among these monarchies, often being considered a diarchy. The King, or Ngwenyama, rules alongside his mother, the Ndlovukati, as dual heads of state originally designed to be checks on political power. The Ngwenyama, however, is considered the administrative head of state, while the Ndlovukati is considered the spiritual and national head of state, a position which more or less has become symbolic in recent years. The Pope is the absolute monarch of the Vatican City State (different entity from the Holy See) by virtue of his position as head of the Roman Catholic Church and Bishop of Rome; he is an elected rather than hereditary ruler and has not to be a citizen of the territory prior to his election by the cardinals.
Some of the extant sovereign monarchies have lines of succession that go back to the medieval period or antiquity:
- Japan, considered a constitutional monarchy under the Imperial House of Japan, has a claim to being the world’s oldest extant continuous hereditary monarchy, with a traditional origin in 660 BC, and reliable historiographical evidence from at least the 6th century.
- The kings of Cambodia claim descent from Queen Soma (1st century), although the historiographical record is interrupted in the “Dark ages of Cambodia” (15th/16th centuries).
- The monarchs of the United Kingdom and Commonwealth realms inherit the throne by virtue of the line of descent from the House of Stuart (Union of the Crowns 1603), combining the lines of succession of the kingdoms of England and Scotland going back to the 9th century. The succession to the English throne can be argued to originate with the House of Wessex, established in the 6th century; that to the Scottish throne with descent from Pictish kings which likewise enter the historical record around the 6th century.
- The monarchs of the kingdom of Norway by virtue of descent from Harald I Fairhair, who united the realm in 872. Harald as a member of the House of Yngling is given a partly legendary line of succession from earlier petty kings in historiographical tradition.
- The kings of Spain via descent from the Catholic Monarchs (via the House of Habsburg), ultimately combining the lines of succession of Castile and León and Aragon, realms established in the 10th to 11th centuries in the course of the Reconquista, via the Kingdom of Asturias claiming descent from the Visigothic Kingdom (which, originally ruled by the Thervingi kings, had become elective in the 6th century).