The Buddhist Uprising of 1966 (Vietnamese: Ni dy Pht gio 1966), or more widely known in Vietnam as the Crisis in Central Vietnam (Vietnamese: Bin ng Min Trung), was a period of civil and military unrest in South Vietnam, largely focused in the I Corps area in the north of the country in central Vietnam. The area is a heartland of Vietnamese Buddhism, and at the time, activist Buddhist monks and civilians were at the forefront of opposition to a series of military juntas that had been ruling the nation, as well as prominently questioning the escalation of the Vietnam War.

During the rule of the Catholic Ng nh Dim, the discrimination against the majority Buddhist population generated the growth of Buddhist institutions as they sought to participate in national politics and gain better treatment. In 1965, after a series of military coups that followed the fall of the Dim regime in 1963, Air Marshal Nguyn Cao K and General Nguyn Vn Thiu finally established a stable junta, holding the positions of Prime Minister and figurehead Chief of State respectively. The K-Thiu regime was initially almost a feudal system, being more of an alliance of warlords than a state as each corps commander ruled his area as his own fiefdom, handing some of the taxes they collected over to the government in Saigon and keeping the rest for themselves. During that time, suspicion and tension continued between the Buddhist and Catholic factions in Vietnamese society.

The religious factor combined with a power struggle between K and General Nguyn Chnh Thi, the commander of I Corps, a Buddhist local to the region and popular in the area. Thi was a strong-willed officer regarded as a capable commander, and K saw him as a threat, as did others within the junta. In February 1966, K attended a summit in Honolulu, where he became convinced that he now had American support to move against Thi, the strongest and most able of the corps commanders. In March 1966, K fired Thi and ordered him into exile in the United States under the false pretense of medical treatment. This prompted both civilians and some I Corps units to launch widespread civil protests against K's regime and halt military operations against Viet Cong. K gambled by allowing Thi to return to I Corps before departing for the US, but the arrival of the general to his native area only fuelled anti-K sentiment. The Buddhist activists, students and Thi loyalists in the military coalesced into the "Struggle Movement", calling for a return to civilian rule and elections. Meanwhile, Thi stayed in I Corps and did not leave; strikes and protests stopped civilian activity in the area, government radio stations were taken over and used for anti-K campaigning, and military operations ceased. Riots also spread to the capital Saigon and other cities further south.

At the start of April, K decided to move. He declared that Da Nang, the main centre in I Corps, was under communist control and publicly vowed to kill the mayor, who had expressed support for the Struggle Movement. K moved military forces into the city and travelled there to prepare for an assault, but had to withdraw and then start discussions with Buddhist leaders, as it was obvious that he was not strong enough to crush the opposition. In the meantime, he fired Thi's successor Nguyn Vn Chun because he wanted a firmer attempt to regain control, and appointed Tn Tht nh to replace him. nh claimed to have calmed the situation, but K viewed the situation as appeasement, and on May 15, his forces drove off nh and took over. During the previous month, American forces had also become involved in the stand-off, and the Struggle Movement viewed their participation as biased towards K, leading to some tense confrontations.

In the second half of May, K's forces began to force the issue and gradually wore down the Struggle Movement as the rebel I Corps forces were worn down, despite some American objections that his aggressive attacks had the potential to cause too much collateral damage. At one stage, K's forces ended up in a skirmish with American forces, and later, the Americans were in the middle of a stand-off between the Vietnamese factions regarding a mined bridge. As K's forces took back Da Nang and Hu in street fighting, Struggle Movement supporters saw American intervention as being pro-K, and anti-US riots resulted in some American buildings being burnt down. K's triumph ended the Buddhist movement's influence on politics and he confined their leader Thch Tr Quang to house arrest thereafter, while Thi left for the US.

South Vietnam, officially the Republic of Vietnam (RVN; Vietnamese: Việt Nam Cộng Hòa; French: République du Viêt Nam), was a country that existed from 1955 to 1975, the period when the southern portion of Vietnam was a member of the Western Bloc during part of the Cold War. It first received international recognition in 1949 as the State of Vietnam within the French Union, with its capital at Saigon (renamed to Ho Chi Minh City in 1976), before becoming a republic in 1955. South Vietnam was bordered by North Vietnam to the north, Laos to the northwest, Cambodia to the southwest, and Thailand across the Gulf of Thailand to the southwest. Its sovereignty was recognized by the United States and 87 other nations, though it failed to gain admission into the United Nations as a result of a Soviet veto in 1957.The end of the Second World War saw anti-Japanese Việt Minh guerrilla forces, led by communist fighter Ho Chi Minh, proclaiming the establishment of the Democratic Republic of Vietnam in Hanoi in September 1945. In 1949, anti-communist politicians formed a rival government in Saigon led by former emperor Bảo Đại. A 1955 referendum on the state's future form of government was highly contested and resulted in the deposal of Bảo Đại by Prime Minister Ngô Đình Diệm, who proclaimed himself president of the new republic on 26 October 1955. After the 1954 Geneva Conference, it abandoned its claims to the northern part of the country and established its sovereignty over the southern half of Vietnam consisting of Cochinchina (Nam Kỳ) – a former French colony and parts of Annam (Trung Kỳ) – a former French protectorate. Diệm was killed in a military coup led by general Dương Văn Minh with help from the CIA in 1963, and a series of short-lived military governments followed. General Nguyễn Văn Thiệu then led the country after a US-encouraged civilian presidential election from 1967 until 1975.

The beginnings of the Vietnam War occurred in 1955 with an uprising by the newly organized National Liberation Front for South Vietnam (Việt Cộng), armed and supported by the North Vietnam, with backing mainly from China and the Soviet Union. Larger escalation of the insurgency occurred in 1965 with American intervention and the introduction of regular forces of Marines, followed by Army units to supplement the cadre of military advisors guiding the Southern armed forces. A regular bombing campaign over North Vietnam was conducted by offshore US Navy airplanes, warships, and aircraft carriers joined by Air Force squadrons through 1966 and 1967. Fighting peaked up to that point during the Tet Offensive of February 1968, when there were over a million South Vietnamese soldiers and 500,000 US soldiers in South Vietnam. What started as a guerrilla war eventually turned into a more conventional fight as the balance of power became equalized. An even larger, armored invasion from the North commenced during the Easter Offensive following US ground-forces withdrawal, and had nearly overran some major northern cities until beaten back.

Despite a truce agreement under the Paris Peace Accords, concluded in January 1973 after five years of on-and-off negotiations, fighting continued almost immediately afterwards. The regular North Vietnamese army and Việt-Cộng auxiliaries launched a major second combined-arms conventional invasion in 1975. Communist forces overran Saigon on 30 April 1975, marking the end of the Republic of Vietnam. On 2 July 1976, North Vietnam-controlled Provisional Revolutionary Government of the Republic of South Vietnam and the Democratic Republic of Vietnam (North Vietnam) merged to form the Socialist Republic of Vietnam.