Forced to abdicate in 1947, King Michael I was the last monarch of which country?

Michael I (born 25 October 1921) reigned as King of Romania from 20 July 1927 to 8 June 1930 and again from 6 September 1940 until his abdication on 30 December 1947.

Shortly after his birth, Michael's father Prince Carol had become involved in a controversial relationship with Magda Lupescu. In 1925, Carol was eventually pressured to renounce his rights to the throne and moved to Paris in exile with Lupescu. In 1927, Michael ascended the throne following the death of his grandfather, Ferdinand I. As he was still a minor, a regency council was instituted. The council proved to be ineffective and in 1930, Carol returned to Romania and replaced his son as king. As a result, Michael returned to being heir apparent to the throne and was given the additional title of Grand Voievod of Alba-Iulia.

Carol II was deposed in 1940, and Michael once again became king. From August 1945 to January 1946, Michael went on a "royal strike" and unsuccessfully tried to oppose Groza's Communist-controlled government by refusing to sign and endorse its decrees. In November, Michael attended the wedding of his cousins, the future Queen Elizabeth II and Prince Philip of Greece in London. Shortly thereafter, on the morning of 30 December 1947, Groza requested a meeting with Michael where he was forced to abdicate. Michael was forced into exile, confiscated of his properties, and stripped of his citizenship.