Sisavang Vatthana or sometimes Savang Vatthana was the last king of the Kingdom of Laos and the 6th Prime Minister of Laos serving from 29 October to 21 November 1951. He ruled from 1959 after his father's death until his forced abdication in 1975. His rule ended with the takeover by the Pathet Lao in 1975, after which he and his family were sent to a re-education camp by the new government.

The Kingdom of Laos was the form of government in Laos from 1947 to 1975. Located in Southeast Asia at the heart of the Indochinese Peninsula, it was bordered by Burma and China to the northwest, North Vietnam to the east, Cambodia to the southeast, and Thailand to the west and southwest. The country was governed as a constitutional monarchy beginning with its independence on 9 November 1953. It survived until December 1975, when its last king, Sisavang Vatthana, surrendered the throne to the Pathet Lao during the civil war in Laos, who abolished the monarchy in favour of a Marxist–Leninist state called the Lao People's Democratic Republic, which has controlled Laos ever since.