The Egyptian–Libyan War or the Four Day War (Arabic: حرب الأربعة أيام) was a short border war fought between Libya and Egypt that lasted from 21 to 24 July 1977. The conflict stemmed from a deterioration in relations that had occurred between the two states after Egyptian President Anwar Sadat had rebuffed Libyan leader Muammar Gaddafi's entreaties to unify their countries and had pursued a peace settlement with Israel in the aftermath of the Yom Kippur War of 1973. Soon thereafter Libya began sponsoring dissidents and assassination plots to undermine Sadat, and Egypt responded in kind to weaken Gaddafi. In early 1976 Gaddafi dispatched troops to the Egyptian frontier where they began clashing with border guards. Sadat responded by moving many troops to the area, while the Egyptian General Staff drew up plans for an invasion to depose Gaddafi.

Clashes along the border intensified in July 1977. On 21 July a Libyan tank battalion raided the town of Sallum. The Egyptian forces ambushed it and subsequently launched a large counter-attack, conducting airstrikes against Gamal Abdel Nasser Airbase and sending a mechanised force 24 kilometres (15 mi) into Libyan territory before withdrawing. Over the next two days heavy artillery fire was exchanged across the border, while Egyptian jets and commandos raided Libyan locales. On 24 July the Egyptians launched a larger raid against Nasser Airbase and struck Libyan supply depots. Under significant pressure from the United States to end the attacks, and attempts from President of Algeria Houari Boumediène and Palestine Liberation Organisation leader Yasser Arafat to mediate a solution, Sadat suddenly declared a ceasefire. Sporadic fighting occurred over the next few days as Egyptian troops withdrew across the border. Relations between the two countries remained tense, and, though a formal agreement was never reached, both upheld a truce and gradually withdrew their forces from the border. Gaddafi softened his rhetoric against Egypt in the following years, but actively rallied other Arab states to isolate the country.