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 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.
The voters of Australia overwhelmingly rejected a proposal to abolish their monarchy in 1999 (rejected in all states, with only the Australian Capital Territory passing the referendum). 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.
Monarchies abolished in the 20th century
Monarchies that were abolished then restored
List of monarchs deposed in the 20th century