The Laotian Civil War (1959–1975) was a civil war in Laos which was waged between the Communist Pathet Lao (including many North Vietnamese of Lao ancestry) and the Royal Lao Government from 23 May 1959 to 2 December 1975. It is associated with the Cambodian Civil War and the Vietnam War, with both sides receiving heavy external support in a proxy war between the global Cold War superpowers. It is called the Secret War among the American CIA Special Activities Center, and Hmong and Mien veterans of the conflict.The Kingdom of Laos was a covert theater for other belligerents during the Vietnam War. The Franco–Lao Treaty of Amity and Association (signed 22 October 1953) transferred remaining French powers to the Royal Lao Government (except control of military affairs), establishing Laos as an independent member of the French Union. However, this government did not include representatives from the Lao Issara anti-colonial armed nationalist movement.The following years were marked by a rivalry between the neutralists under Prince Souvanna Phouma, the right wing under Prince Boun Oum of Champassak, and the left-wing Lao Patriotic Front under Prince Souphanouvong and half-Vietnamese future Prime Minister Kaysone Phomvihane. Several attempts were made to establish coalition governments, and a "tri-coalition" government was finally seated in Vientiane.

The fighting in Laos involved the North Vietnamese Army, U.S. troops and Thai forces and South Vietnamese army forces directly and through irregular proxies in a struggle for control over the Laotian Panhandle. The North Vietnamese Army occupied the area to use for its Ho Chi Minh Trail supply corridor and as staging area for offensives into South Vietnam. There was a second major theater of action on and near the northern Plain of Jars.

The North Vietnamese and Pathet Lao eventually emerged victorious in 1975, as part of the general communist victory in all of former French Indochina that year. A total of up to 300,000 people from Laos fled to neighbouring Thailand following the Pathet Lao takeover.After the communists took power in Laos, Hmong rebels fought the new government. The Hmong were persecuted as traitors and "lackeys" of the Americans, with the government and its Vietnamese allies carrying out human rights abuses against Hmong civilians. The incipient conflict between Vietnam and China also played a role with Hmong rebels being accused of receiving support from China. Over 40,000 people died in the conflict.The Lao royal family were arrested by the Pathet Lao after the war and sent to labor camps, where most of them died in the late 1970s and 1980s, including King Savang Vatthana, Queen Khamphoui and Crown Prince Vong Savang.