The Kingdom of Laos was a constitutional monarchy that ruled Laos beginning with its independence on November 9, 1953. The monarchy survived until December 1975 when its last king, Savang Vatthana, surrendered the throne to the Pathet Lao, who abolished the monarchy in favor of a Marxist state called the Lao People's Democratic Republic which has controlled Laos since.
Given self-rule with the new Constitution in 1947 as part of a federation with the rest of French Indochina, the 1953 Franco-Lao Treaty finally established a sovereign, independent Laos, but did not stipulate who would rule the country. In the years that followed, three groups led by the so-called Three Princes, contended for power: the neutralists under Prince Souvanna Phouma, the right-wing party under Prince Boun Oum of Champassak, and the left-wing, Vietnamese-backed Lao Patriotic Front (now called the Pathet Lao) under Prince Souphanouvong and future Prime Minister Kaysone Phomvihane.