Laotian political leader and revolutionary who was a communist leader from 1955 and, following the overthrow of the 600-year-old monarchy (1975), ruler of Laos.

Kaysone was born in southern Laos of a Lao mother and a Vietnamese father, a civil servant in the French colonial government. Kaysone protested against Japanese occupation of his country during World War II, and while studying law at the University of Hanoi, he became involved with the nascent Indochinese Communist Party. He was sent back to Laos by Ho Chi Minh to join the anti-French revolutionary movement that was later known as the Pathet Lao.

In 1955 Kaysone helped found and became general secretary of what was later called the Lao People's Revolutionary Party. In 1958 he unsuccessfully ran for a seat in the Supreme People's Assembly. After the resumption of hostilities in 1964, he moved the Pathet Lao into caves in the northern mountains, withstanding the United States' carpet bombing of the area. After the disintegration of a short-lived, U.S.-backed postwar government in 1975, he became prime minister of the newly created Lao People's Democratic Republic. He was one of the leaders responsible for allowing King Savang Vatthana and Queen Khamphouis to perish in a detention camp, reportedly in 1981. He kept the country closely allied with Vietnam and isolated from Western influence until the end of the Cold War, when he sought new financial aid by visiting France and Japan in 1989. After a new constitution was adopted in 1991, he became president, and the following year he relaxed some government controls and scheduled elections for the Supreme People's Assembly. He also released most political prisoners, including those army officers from the pro-Western regime held in detention camps since 1975, and he also distanced Laos from Vietnam by improving relations with China.