A personal union consists of two or more entities that are internationally considered separate states, only sharing the same Head of State (and thence also sharing whatever political actions are vested in the Head of State, but no, or at least extremely few, others). It is not to be confused with a federation (like the United States), which is internationally considered a single state.

Personal unions can arise for very different reasons, ranging from near coincidence (a princess who is already married to a king becomes a queen regnant, and their child inherits the crown of both countries) to virtual annexation (where a personal union sometimes was seen as a means of preventing uprisings). They can also be codified (the constitutions of the states clearly express that they shall be joined together) or non-codified (in which case they can easily be broken by e.g. different succession rules).

Because presidents of republics are ordinarily chosen from within the citizens of the state in question, personal unions are almost entirely a phenomenon of monarchies. With the decline of their number during the 20th century, personal unions have become quite uncommon. Where they do exist, most notably between the so-called Commonwealth Realms, they are now mostly ceremonial, as the Governor-General, in theory the representative of the Head of State, has only marginal political power, and is nominated by and has to take the advice of the local Head of Government.

There is a somewhat grey area between personal unions and federations, and the one has regularly grown into the other. This article is an attempt at listing some historical and contemporary personal unions.

Albania

• Personal union (not universally recognized) with Italy from 1939 to 1946 (when republic was proclaimed)
• Personal union (not universally recognized) with Ethiopia from 1939 to 1941

Andorra

• Partial personal union with France since 1607 (the French president, and formerly the king of France, is one of the Heads of State in Andorra)

Antigua and Barbuda

• The Commonwealth Realms, officially a personal union since 1927, presently unifies Antigua and Barbuda, Australia, the Bahamas, Barbados, Belize, Canada, Grenada, Jamaica, New Zealand, Papua New Guinea, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines, the Solomon Islands, Tuvalu and the United Kingdom

Australia

• The Commonwealth Realms, officially a personal union since 1927 (see Antigua and Barbuda, above, for participants)

Austria

• Personal union with Hungary from 1867 to 1918 (the dual monarchy of Austria-Hungary)

Bahamas

• The Commonwealth Realms, officially a personal union since 1927 (see Antigua and Barbuda, above, for participants)

Barbados

• The Commonwealth Realms, officially a personal union since 1927 (see Antigua and Barbuda, above, for participants)

Belize

• The Commonwealth Realms, officially a personal union since 1927 (see Antigua and Barbuda, above, for participants)

Canada

• The Commonwealth Realms, officially a personal union since 1927 (see Antigua and Barbuda, above, for participants)

Denmark

• Personal union with Norway from 1380 to 1536 (when Norway was officially incorporated into the Danish kingdom, often called Denmark-Norway)
• The Kalmar Union with Norway and Sweden from 1389 to 1521 (sometimes defunct)
• The kings of Denmark at the same time being dukes of Schleswig and Holstein 1460-1864. (Holstein being part of the Holy Roman Empire)
• Personal union with Iceland from 1918 (broken out of Denmark) to 1944

England

• Personal union with Ireland from 1541 (when Ireland was raised to the level of a kingdom) to 1707
• Personal union with Scotland from 1603 to 1707 (when they were joined together in the Kingdom of Great Britain)
• Personal union with the Netherlands from 1689 to 1702, with the King of England, Scotland and Ireland also serving as Stadtholder of most of the provinces of the Netherlands. The actual situation was slightly more complex with the Dutch provinces Holland, Zeeland and Utrecht entering into personal union in 1672, Gelderland and Overijssel in 1675 and Drenthe in 1696. Only 2 Dutch provinces never entered into the personal union: Friesland and Groningen.

Ethiopia

• Personal union (not universally recognized) with Italy from 1936 to 1941
• Personal union (not universally recognized) with Albania from 1939 to 1941

Finland

• Personal union with Russia from 1809 (ceded from Sweden) to 1917

France

• Partial personal union with Andorra since 1607 (the French president is one of the Heads of State in Andorra)

Great Britain

• Personal union with Ireland from 1707 to 1801 (when they were joined together in the United Kingdom of Great Britain and Ireland)
• Personal union with Hanover from 1714 to 1801

Grenada

• The Commonwealth Realms, officially a personal union since 1927 (see Antigua and Barbuda, above, for participants)

Hanover

• Personal union with Great Britain and Ireland from 1714 to 1801
• Personal union with the United Kingdom from 1801 to 1837

Holy Roman Empire

• Personal union with Spain from 1519 to 1556

Hungary

• Personal union with Austria from 1867 to 1918 (the dual monarchy of Austria-Hungary)

Iceland

• Personal union with Denmark from 1918 (broken out of Denmark) to 1944

Ireland

• Personal union with England from 1541 (raised to the level of a kingdom) to 1707
• Personal union with Scotland from 1603 to 1707
• Personal union with the Netherlands from 1689 to 1702, with the King of England, Scotland and Ireland also serving as Stadtholder of most of the provinces of the Netherlands. The actual situation was slightly more complex with the Dutch provinces Holland, Zeeland and Utrecht entering into personal union in 1672, Gelderland and Overijssel in 1675 and Drenthe in 1696. Only 2 Dutch provinces never entered into the personal union: Friesland and Groningen.
• Personal union with Great Britain from 1707 to 1801 (when they were joined together in the United Kingdom of Great Britain and Ireland)
• Personal union with Hanover from 1714 to 1801
• Personal union with the United Kingdom from 1922 (broken out) to 1949

Italy

• Personal union (not universally recognized) with Ethiopia from 1936 to 1941
• Personal union (not universally recognized) with Albania from 1939 to 1946

Jamaica

• The Commonwealth Realms, officially a personal union since 1927 (see Antigua and Barbuda, above, for participants)

Lithuania

• Personal union with Poland from 1386 to 1569 (when they were joined together in the Polish-Lithuanian Commonwealth)

Luxembourg

• Personal union with the Netherlands from 1815 to 1890

New Zealand

• The Commonwealth Realms, officially a personal union since 1927 (see Antigua and Barbuda, above, for participants)

Norway

• Personal union with Sweden from 1319 to 1343
• Personal union with Denmark from 1380 to 1536 (when Norway was officially incorporated into the Danish kingdom, often called Denmark-Norway)
• The Kalmar Union with Denmark and Sweden from 1389 to 1521 (sometimes defunct)
• Personal union with Sweden from 1814 to 1905 (when Norway was ceded from Denmark and entered into a union with Sweden, sometimes called Sweden-Norway)

Netherlands

• Personal union with England, Scotland and Ireland from 1672 to 1702, with the King of England, Scotland and Ireland also serving as Stadtholder of most of the provinces of the Netherlands. The actual situation was slightly more complex with the Dutch provinces Holland, Zeeland and Utrecht entering into personal union in 1672, Gelderland and Overijssel in 1675 and Drenthe in 1696. Only 2 Dutch provinces never entered into the personal union: Friesland and Groningen.
• Personal union with Luxembourg from 1815 to 1890.

Papua New Guinea

• The Commonwealth Realms, officially a personal union since 1927 (see Antigua and Barbuda, above, for participants)

Poland

• Personal union with Lithuania from 1386 to 1569 (when they were joined together in the Polish-Lithuanian Commonwealth)

Poland-Lithuania

• Personal union with Sweden from 1592 to 1599

Portugal

• Personal union with Spain from 1580 to 1640 (under Philip II of Spain, his son and grandson)

Russia

• Personal union with Finland from 1809 to 1917

Saint Kitts and Nevis

• The Commonwealth Realms, officially a personal union since 1927 (see Antigua and Barbuda, above, for participants)

Saint Lucia

• The Commonwealth Realms, officially a personal union since 1927 (see Antigua and Barbuda, above, for participants)

Saint Vincent and the Grenadines

• The Commonwealth Realms, officially a personal union since 1927 (see Antigua and Barbuda, above, for participants)

Scotland

• Personal union with England and Ireland from 1603 to 1707 (when England and Scotland were joined together in the Kingdom of Great Britain)
• Personal union with the Netherlands from 1689 to 1702, with the King of England, Scotland and Ireland also serving as Stadtholder of most of the provinces of the Netherlands. The actual situation was slightly more complex with the Dutch provinces Holland, Zeeland and Utrecht entering into personal union in 1672, Gelderland and Overijssel in 1675 and Drenthe in 1696. Only 2 Dutch provinces never entered into the personal union: Friesland and Groningen.

Spain

• Personal union with the Holy Roman Empire from 1519 to 1556
• Personal union with Portugal from 1580 to 1640 (under Philip II of Spain, his son and grandson)

Schleswig and Holstein

Duchies with peculiar rules for succession.

• 1460 to 1864 parts or all of the duchies in personal union with Denmark.

Solomon Islands

• The Commonwealth Realms, officially a personal union since 1927 (see Antigua and Barbuda, above, for participants)

Sweden

Main article: Unions of Sweden

• Personal union with Norway from 1319 to 1343
• The Kalmar Union with Denmark and Norway from 1389 to 1521 (sometimes defunct)
• Personal union with Poland-Lithuania from 1592 to 1599
• Personal union with Norway from 1814 to 1905 (sometimes called Sweden-Norway)

Tuvalu

• The Commonwealth Realms, officially a personal union since 1927 (see Antigua and Barbuda, above, for participants)

United Kingdom

• Personal union with Hanover from 1801 to 1837
• Personal union with Ireland from 1922 (broken out) to 1949
• The Commonwealth Realms, officially a personal union since 1927 (see Antigua and Barbuda, above, for participants)