The following monarchs either lost their thrones through deposition by a coup, by a referendum which abolished their throne, or chose to abdicate during the twentieth century.
Queen Sisowath Monivong Kossamak - deposed in 1970 with the coup that ended the regime of Prince Norodom Sihanouk. The monarchy was restored in 1993 with Sihanouk (who had previously reigned as King from 1941 to 1955) as King.
The Axis puppet King Tomislav II (Prince Aimone of Savoy, Duke of Spoleto), who had never actually reigned, abdicated in 1943, when Italy made peace with the allies.
King Farouk abdicated, in 1952 in favor of his son Fuad II. Young Fuad was deposed the next year, and Egypt became a republic. (Farouk died 1965, Fuad is still living)
Grand Duke Nicholas II abdicated March 1917. The Russian Provisional Government[?] continues to exercise grand ducal authority for its brief existence.
With the end of World War I, the king-elect, Prince Friedrich Karl of Hesse, was deposed without having ever reigned.
King-Emperor Charles IV - refused permission to assume residency and constitutional functions in the Kingdom of Hungary following the end of World War I by the Regent of Hungary. Died in exile in 1922. Kingdom of Hungary abolished by communists following World War II.
King George VI of the United Kingdom, Emperor of India - ceased to be Emperor in 1947, when India gained its independence, and ceased to be King of India in 1950, when India became a republic. (d.1952)
the last Grand Duke, Adolf Friedrich VI[?], committed suicide in February 1918. From then until the abolition of the monarchy in 1918, the Grand Duke of Mecklenburg-Schwerin acted as regent.
The German and Austrian established Kingdom of Poland, which never had a King, although Archduke Karl Stefan of Austria was for a time King-elect, ceased to exist after the armistice in 1918.
Emperor Nicholas II - abdicated after the February Revolution of 1917, as did his named successor, his brother, Michael II (known for a very short time as Michael II); both Nicholas II and Michael separately were later murdered, as was all of Nicholas II's family. The monarchy was abolished and replaced by a Russian republic under Lenin, which in 1922 became the Soviet Union
Tsar Nicholas II of Russia overthrown by revolution in 1917 executed with his family in 1918
King Alfonso XIII - fled following republican win in local elections in 1931, died 1941 (monarchy restored in 1975 under his grandson, King Juan Carlos)
Queen Elizabeth II of Fiji, Mauritius, South Africa, Pakistan, Sri Lanka, Ghana, Nigeria, Sierra Leone, Gambia, Kenya, Uganda, Tanzania, Malawi, Guyana, Trinidad and Tobago, and Malta (b. 1926)
King Simeon II of Bulgaria (b. 1937) - currently serving as Prime Minister
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