The Western Sahara War was an armed struggle between the Sahrawi indigenous Polisario Front and Morocco from 1975 to 1991, being the most significant phase of the Western Sahara conflict. The conflict erupted after the withdrawal of Spain from the Spanish Sahara in accordance with the Madrid Accords, by which it transferred administrative control of the territory to Morocco and Mauritania, but not sovereignty. In late 1975, the Moroccan government organized the Green March of some 350,000 Moroccan citizens, escorted by around 20,000 troops, who entered Western Sahara, trying to establish a Moroccan presence. While at first met with just minor resistance by the Polisario Front, Morocco later engaged a long period of guerrilla warfare with the Sahrawi nationalists. During the late 1970s, the Polisario Front, desiring to establish an independent state in the territory, attempted to fight both Mauritania and Morocco. In 1979, Mauritania withdrew from the conflict after signing a peace treaty with the Polisario Front. The war continued in low intensity throughout the 1980s, though Morocco made several attempts to take the upper hand in 1989–1991. A cease-fire agreement was finally reached between the Polisario Front and Morocco in September 1991. Some sources put the final death toll between 10,000 and 20,000 people.

Western Sahara is a disputed territory on the northwest coast of Africa. About 20% of the territory is controlled by the Sahrawi Arab Democratic Republic (SADR); the remaining 80% is occupied and administered by neighboring Morocco. It has a surface area of 266,000 square kilometres (103,000 sq mi). It is the second most sparsely populated country in the world and most sparsely in Africa, mainly consisting of desert flatlands. The population is estimated at about 500,000, of which nearly 40% live in Morocco-controlled Laayoune, the largest city in Western Sahara.