Personal unions can arise for very different reasons, ranging from near coincedence (a princess who is already married to a king becomes a queen regnant, and their child inherits both countries) to virtual annexation (where a personal union sometimes was seen as a means of preventing uprisals). 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).

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.

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

• 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 Great Britain)

• Finland
  • Personal union with Russia from 1809 (ceded from Sweden) to 1918

• 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

• 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

• 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 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

• 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

• 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 (ceded from Denmark) to 1905

• Netherlands
  • Personal union with Luxembourg from 1815 to 1890

• 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

• Russia
  • Personal union with Finland from 1809 to 1918

• Scotland
  • Personal union with England and Ireland from 1603 to 1707 (when England and Scotland were joined together in Great Britain)

• Spain
  • Personal union with the Holy Roman Empire from 1519 to 1556

• Schleswig and Holstein (Duchies with peculiar rules for succession.)
  • 1460 to 1864 were parts or all of the duchies in personal union with Denmark.

• 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

• 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, presently with 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 and Tuvalu