Throughout history, many of the world's monarchies have been abolished, either through legislative reforms, coups d'etat, or wars.

The first well-known abolition of a modern law-based monarchy occurred in 1649 when Oliver Cromwell successfully led a rebellion that briefly overthrew the English and Scottish monarchies, with the execution of King Charles I. The most famous monarchical abolition occurred in 1792 when the French monarchy was abolished during the French Revolution.

The monarchy in the Thirteen Colonies that became the United States of America were abolished in 1776 when they unilaterally declared their independence from Great Britain. The United States also took part in a coups d'etat that led to the abolition of the monarchy of Hawaii.

The monarchy of Portugal was abolished prior to World War I. The monarchies of Russia, Turkey, Germany, Hungary and Austria were abolished in the aftermath of World War I. Those of Bulgaria, Romania, Albania, and Italy were abolished in the aftermath of World War II.

In the end of World War I, monarchies were planned for the Grand Duchy of Finland (Väinö I of Finland), and for Lithuania (Mindove II of Lithuania ), with a protectorate-like dependency of Germany. Both kings denounced their thrones after Germany's defeat in November 1918.

The Commonwealth Realm monarchies of India, Kenya, Tanzania, South Africa, Zambia, and Zimbabwe were abolished when or shortly after they became independent of the United Kingdom, while remaining within the commonwealth in the middle of the 20th century. That of Ireland was not abolished when Ireland became independent of Britain in the 1920s, but was abolished by the Republic of Ireland Act of 1948, which came into force in 1949.

That of Egypt was abolished after a coup d'etat in 1952, that of Iran was abolished by the Islamic revolution of 1979.

Brazil rejected an attempt to restore its monarchy in the 1990s, while efforts to restore the monarchies of some of the Balkan states in the former Eastern Bloc continue. In Bulgaria Simeon Saxe-Coburg Gotha, who was deposed from the Bulgarian throne in 1946, has been elected and currently serves as the Prime Minister of his country.

In a 1999 referendum, the voters of Australia narrowly rejected a proposal to abolish their monarchy in favour of a specific republic model. The proposal was rejected in all states, with only the Australian Capital Territory passing the proposal, despite surveys indicating that a majority of Australians support Australia becoming a republic; it appears that Australian voters rejected the specific model proposed, rather than the idea of becoming a repbulic.

Monarchies abolished in the 20th century

• Portugal, 1910
• Korea, 1910
• China, 1912 (coup d'etat)
• Russia, 1917 (revolution)
• Germany, 1918
  • Prussia, 1918
  • Bavaria, 1918
  • Württemberg, 1918
  • Saxony, 1918
  • Hesse and by Rhine, 1918
  • Baden, 1918
  • Saxe-Weimar-Eisenach, 1918
  • Mecklenburg-Schwerin, 1918
  • Mecklenburg-Strelitz, 1918
  • Oldenburg, 1918
  • Brunswick, 1918
  • Anhalt, 1918
  • Saxe-Coburg and Gotha, 1918
  • Saxe-Meiningen, 1918
  • Saxe-Altenburg, 1918
  • Waldeck-Pyrmont, 1918
  • Lippe, 1918
  • Schaumburg-Lippe, 1918
  • Schwarzburg-Rudolstadt, 1918
  • Schwarzburg-Sondershausen, 1918
  • Reuss Senior Line, 1918
  • Reuss Junior Line, 1918
• Austria, 1918
• (Finland, 1918 - never in effect)
• (Lithuania, 1918 - never in effect)
• Poland, (Regency Kingdom of Poland (1916-1918)), 1918
• Hungary, 1918 (restored 1920, although throne remained vacant)
• Turkey, 1922 (coup d'etat)
• Greece, 1924 (restored 1935)
• Yugoslavia, 1945
• Iceland, 1944
• Hungary, 1944
• Vietnam, 1945
• Italy, 1946 (referendum)
• Bulgaria, 1946
• Albania, 1946
• Romania, 1947
• Indian Princely States, 1947-1950
• India, 1950
• Egypt, 1953 (coup d'etat)
• Pakistan, 1956
• Tunisia, 1957
• Iraq, 1958 (coup d'etat)
• South Africa, 1961
• Yemen, 1962
• Burundi, 1966
• Maldives, 1968
• Libya, 1969 (coup d'etat)
• Greece, 1973 (coup d'etat, confirmed by referendum 1974)
• Afghanistan, 1973 (coup d'etat)
• Ethiopia, 1974 (coup d'etat)
• Malta, 1974
• Laos, 1975 (coup d'etat)
• Iran, 1979 (revolution)
• Fiji, 1987 (coup d'etat)
• Mauritius, 1992

Monarchies that were abolished then restored

• Spain, deposed 1931, restored 1975
• Cambodia, deposed 1960, restored 1993
• Ugandan traditional states of Buganda, Toro, Bunyoro, Ankole, and were abolished in 1967 and the restored in 1993

See also

• List of monarchs deposed before the 17th century
• list of monarchs deposed in the 17th century
• List of monarchs deposed in the 18th century
• List of monarchs deposed in the 19th century
• List of monarchs deposed in the 20th century
• List of extinct states