The Battle of Lộc Ninh was a major battle of the Vietnam War fought during the Easter Offensive, which took place in Bình Long Province, South Vietnam between 4 and 7 April 1972. Towards the end of 1971, North Vietnamese leaders decided to launch a major offensive against South Vietnam, with the objective of destroying Army of the Republic of Vietnam (ARVN) units and capturing as much territory as possible, in order to strengthen their bargaining position in the Paris Peace Accords. On 30 March 1972, two People's Army of Vietnam (PAVN) divisions smashed through the Vietnamese Demilitarized Zone, marking the commencement of the Easter Offensive. They quickly overwhelmed South Vietnamese units in the I Corps Tactical Zone. With the rapid collapse of South Vietnamese forces in the northern provinces of South Vietnam, PAVN and Viet Cong (VC) forces began preparing for their next offensive, targeting Bình Long Province in the rubber plantation region north of Saigon. On 4 April, the VC 5th Division opened their attack on Lộc Ninh, defended by the ARVN 9th Infantry Regiment. After three days of fighting, the vastly outnumbered ARVN forces, though well supported by American air power, were forced to abandon their positions in Lộc Ninh.

In December 1971, following the defeat of South Vietnamese forces during Operation Lam Son 719, North Vietnamese leadership in Hanoi decided to launch a major military offensive against South Vietnam. In what became known as the Easter Offensive, the combined PAVN and VC forces employed combined arms tactics using heavy weapons that were a radical departure from the low-intensity guerrilla warfare of previous years. Although North Vietnam eventually used the equivalent of 14 army divisions, its leaders did not seek to win the war outright. Rather, their objective was to gain as much territory and destroy as many units of the South Vietnamese military as possible, in order to strengthen their bargaining position at the Paris Peace Talks.

The Easter Offensive began on 30 March 1972, when the PAVN 304th and 308th Divisions drove across the Demilitarized Zone and attacked ARVN positions in the I Corps Tactical Zone, which consisted of South Vietnam's northernmost provinces. Caught by surprise, ARVN General Vũ Văn Giai ordered his newly created 3rd Infantry Division to withdraw towards the Cua Viet River, where it could reorganize.

On 2 April, ARVN Colonel Pham Van Dinh surrendered his 56th Infantry Regiment at Camp Carroll, which enabled the PAVN to take the former American fire base without a fight. Quảng Trị City was captured by the PAVN on 28 April, following several counterattacks by ARVN units around Đông Hà.

With the northern provinces of South Vietnam under their control, PAVN forces turned their attention to the Cambodian border region north of Saigon, which formed part of the ARVN III Corps Tactical Zone. During the offensive, the objective of the PAVN/VC in the zone was the capture of An Lộc, capital of Bình Long Province. The VC committed three infantry divisions to the mission (5th, 7th and 9th Divisions). PAVN forces comprised one artillery formation (69th Artillery Command), one armored regiment (203rd Armored Regiment), two independent regiments (205th and 101st Regiment), and one sapper unit (429th Sapper Group). The VC 5th Division was to initiate the offensive by taking Lộc Ninh, while the 9th Division was assigned to An Lộc. The 7th Division was ordered to block National Highway 13 to prevent reinforcements from reaching An Lộc.

In late December 1971, ARVN intelligence in the III Corps had detected the buildup of PAVN/VC formations across the border in neighbouring Cambodia. Even though it was obvious that preparations for a major offensive were under way, ARVN commanders were unable to predict the PAVN/VC's intentions. In January 1972, the VC 5th Division was reported to have taken up positions in Snuol, a Cambodian city located about 30 kilometres (19 mi) west of Lộc Ninh. South Vietnamese intelligence also detected the presence of the VC 7th and 9th Divisions in Dambe and Chup respectively. Between January and May 1971, the ARVN mounted Operation Toan Thang TT02, with the aim of destroying VC main force divisions based in Cambodia, specifically in the Snuol area. But due to the death of General Đỗ Cao Trí, the commander of III Corps, in a helicopter accident, the ARVN were forced to retreat from Snuol without achieving their objective.

In February and March 1972, ARVN units patrolling the border with Cambodia detected increased PAVN/VC activity in the Fishhook area, most notably the presence of the VC 5th Division in an area north of Bình Long Province. On 13 March, an ARVN mechanized task force operating in Cambodia discovered a huge depot that contained large quantities of assault rifles, machine guns, rockets, anti-aircraft guns and ammunition in Base Area 354 (Svay Rieng Province) and Base Area 708 (Kampong Cham Province). On 27 March, a VC deserter from a reconnaissance company of the 7th Division revealed that his unit was surveying a portion of road between Tây Ninh and Bình Long in preparation for its next move. Between 27 March and 1 April, more enemy prisoners and documents were captured by the ARVN, which revealed that the VC 7th and 9th Divisions were coordinating their efforts against an unidentified target.

The movements of PAVN/VC forces near the Cambodian-South Vietnamese border during the first three months of 1972 clearly indicated that a major offensive was in the making. However, the whereabouts of the next thrust was the topic that concerned South Vietnamese and U.S. intelligence officers the most. In previous offensives, the PAVN/VC had used Tây Ninh as an invasion route, as it was surrounded by VC bases in War zone C, the Iron Triangle and the Parrot's Beak, Cambodia. South Vietnamese and U.S. military intelligence reached a consensus that Tây Ninh would be the next target for the Easter Offensive. To reinforce that perception, on 2 April, the VC 24th Independent Regiment overran Fire Support Base Lac Long, defended by elements of the ARVN 49th Infantry Regiment, 5th Infantry Division, about 35 kilometres (22 mi) northwest of Tây Ninh.