The Battle of Lukaya (Kiswahili: Mapigano ya Lukaya) was a battle of the Uganda–Tanzania War. It was fought on 10 and 11 March 1979 around Lukaya, Uganda, between Tanzanian forces (supported by Ugandan rebels) and Ugandan government forces (supported by Libyan and Palestinian troops). After briefly occupying the town, Tanzanian troops and Ugandan rebels retreated under artillery fire. The Tanzanians subsequently launched a counterattack, retaking Lukaya and killing hundreds of Libyans and Ugandans.

President Idi Amin of Uganda had attempted to invade neighbouring Tanzania to the south in 1978. The attack was repulsed, and Tanzania launched a counterattack into Ugandan territory. In February 1979, the Tanzania People's Defence Force (TPDF) seized Masaka. The TPDF's 201st Brigade was then instructed to secure Lukaya and its causeway to the north, which served as the only direct route through a large swamp to Kampala, the Ugandan capital. Meanwhile, Amin ordered his forces to recapture Masaka, and a force was assembled for the purpose consisting of Ugandan troops, allied Libyan soldiers, and a handful of Palestine Liberation Organisation guerrillas, led by Lieutenant Colonel Godwin Sule.

On the morning of 10 March, the TPDF's 201st Brigade under Brigadier Imran Kombe, bolstered by a battalion of Ugandan rebels, occupied Lukaya without incident. In the late afternoon the Libyans attacked the town with rockets, and the unit broke and fled into the nearby swamp. Tanzanian commanders ordered the 208th Brigade to march to the Kampala road to flank the Ugandan-Libyan force. At dawn on 11 March the 208th Brigade reached its target position and the Tanzanian counterattack began. The regrouped 201st Brigade assaulted the Libyans and Ugandans from the front and the 208th from their rear. Sule was killed, precipitating the collapse of the Ugandan defences, while the Libyans retreated. Hundreds of Ugandan government and Libyan troops were killed. The Battle of Lukaya was the largest engagement of the war. Amin's forces were adversely affected by the outcome, and Ugandan resistance crumbled in its wake. The TPDF was able to proceed up the road and later attack Kampala.

In 1971, Colonel Idi Amin launched a military coup that overthrew the President of Uganda, Milton Obote, precipitating a deterioration of relations with neighbouring Tanzania. Tanzanian President Julius Nyerere had close ties with Obote and had supported his socialist orientation. Amin installed himself as President of Uganda and ruled the country under a repressive dictatorship. Nyerere withheld diplomatic recognition of the new government and offered asylum to Obote and his supporters. He tacitly supported a failed attempt by Obote to overthrow Amin in 1972, and after a brief border conflict he and Amin signed a peace accord. Nevertheless, relations between the two presidents remained tense, and Amin made repeated threats to invade Tanzania.

Uganda's economy languished under Amin's corrupt rule, and instability manifested in the armed forces. Following a failed mutiny in late October 1978, Ugandan troops crossed over the Tanzanian border in pursuit of rebellious soldiers. On 1 November Amin announced that he was annexing the Kagera Salient in northern Tanzania. Tanzania halted the sudden invasion, mobilised anti-Amin opposition groups, and launched a counteroffensive. Nyerere told foreign diplomats that he did not intend to depose Amin, but only "teach him a lesson". The claim was not believed; Nyerere despised Amin, and he made statements to some of his colleagues about overthrowing him. The Tanzanian Government also felt that the northern border would not be secure unless the threat presented by Amin was eliminated. After the Tanzania People's Defence Force (TPDF) retook northern Tanzania, Major General David Musuguri was appointed commander of the 20th Division and ordered to push into Ugandan territory. In-mid February, Libyan troops were flown into Entebbe to assist the Uganda Army. Libyan leader Muammar Gaddafi felt that Uganda, a Muslim state in his view, was being threatened by a Christian army, and wished to halt the Tanzanians.

On 24 February 1979, the TPDF seized Masaka. Nyerere originally planned to halt his forces there and allow Ugandan exiles to attack Kampala, the Ugandan capital, and overthrow Amin. He feared that scenes of Tanzanian troops occupying the city would reflect poorly on the country's image abroad. However, Ugandan rebel forces did not have the strength to defeat the incoming Libyan units, so Nyerere decided to use the TPDF to take the capital. The fall of Masaka surprised and troubled Ugandan commanders, who felt that the defeat made Kampala vulnerable to attack. They mobilised additional forces and began planning for a defence of the city. The Uganda Army also showed first signs of disintegrating, as various high-ranking commanders disappeared or were murdered. One Ugandan soldier stated in an interview with Drum, a South African magazine, that "the situation is worsening every day and therefore our days are numbered". Meanwhile, the TPDF's 20th Division prepared to advance from Masaka to Kampala.

The only road from Masaka to Kampala passed through Lukaya, a town 39 kilometres (24 mi) to the north of the former. From there, the route continued on a 25-kilometre (16 mi) causeway that went through a swamp until it reached Nabusanke. The swamp was impassable for vehicles, and the destruction of the causeway would delay a Tanzanian attack on Kampala for months. Though the TPDF would be vulnerable on the passage, Musuguri ordered his troops to secure it. The TPDF's 207th Brigade was dispatched through the swamp to the east, the 208th Brigade was sent west to conduct a wide sweep that would bring it around the northern end of the swamp, and the 201st Brigade under Brigadier Imran Kombe was to advance up the road directly into the town. The 201st consisted almost entirely of militiamen, many of whom had not seen combat. However, the unit was bolstered by a battalion of Ugandan rebels, led by Lieutenant Colonel David Oyite-Ojok.

A plan to destroy the causeway was presented to Amin in Kampala, but he rejected it, saying that it would inhibit his army's ability to launch a counteroffensive against the Tanzanians. He also believed that with Libyan support the TPDF would soon be defeated, and thus destroying and then rebuilding the causeway later would be unnecessary. According to diplomats, Amin initially planned to make a defensive "last stand" at Mpigi, a town located south of Kampala and north of Lukaya. On 2–4 March, the Uganda Army defeated a rebel attack during the Battle of Tororo, heartening Amin. Along with his commanders' urgings, the victory at Tororo persuaded the President to order a counteroffensive. On 9 March over a thousand Libyan troops and about 40 Palestine Liberation Organisation (PLO) guerrillas belonging to Fatah were flown into Uganda. They reinforced the about 400 PLO militants who were already in the country. The Libyan force included regular units, sections of the People's Militia, and members of the Pan-African Legion. They were accompanied by 15 T-55 tanks, over a dozen armoured personnel carriers, multiple Land Rovers equipped with 106 mm (4.2 in) recoilless rifles, one dozen BM-21 Grad 12-barrel Katyusha rocket launcher variants, and other large artillery pieces, such as 122 mm mortars and two batteries of D-30 howitzers. The PLO forces were commanded by Colonel Mutlaq Hamdan (alias "Abu Fawaz"), Major Wassef Erekat, Captain Juma Hassan Hamdallah, and Captain Ibrahim Awad.