The Angolan Civil War was a major civil conflict in the Southern African state of Angola, beginning in 1975 and continuing, with some interludes, until 2002. The war began immediately after Angola became independent from Portugal in November 1975. Prior to this, a decolonisation conflict had taken place in 1974–75, following the Angolan War of Independence. The Civil War was primarily a struggle for power between two former liberation movements, the People's Movement for the Liberation of Angola (MPLA) and the National Union for the Total Independence of Angola (UNITA). At the same time, it served as a surrogate battleground for the Cold War, due to heavy intervention by major opposing powers such as the Soviet Union and the United States.

Each organisation had different roots in the Angolan social fabric and mutually incompatible leaderships, despite their sharing the aim of ending colonial occupation. Although both the MPLA and UNITA had socialist leanings, for the purpose of mobilising international support they posed as "Marxist-Leninist" and "anti-communist", respectively. A third movement, the National Front for the Liberation of Angola (FNLA), having fought the MPLA alongside UNITA during the war for independence and the decolonization conflict, played almost no role in the Civil War. Additionally, the Front for the Liberation of the Enclave of Cabinda (FLEC), an association of separatist militant groups, fought for the independence of the province of Cabinda from Angola.

A civil war is a war between organized groups within the same nation state or republic, or, less commonly, between two countries created from a formerly united nation state. The aim of one side may be to take control of the country or a region, to achieve independence for a region, or to change government policies. The term is a calque of the Latin bellum civile which was used to refer to the various civil wars of the Roman Republic in the 1st century BC.

A civil war is a high-intensity conflict, often involving regular armed forces, that is sustained, organized and large-scale. Civil wars may result in large numbers of casualties and the consumption of significant resources.

Civil wars since the end of World War II have lasted on average just over four years, a dramatic rise from the one-and-a-half year average of the 1900-1944 period. While the rate of emergence of new civil wars has been relatively steady since the mid-19th century, the increasing length of those wars resulted in increasing numbers of wars ongoing at any one time. For example, there were no more than five civil wars underway simultaneously in the first half of the 20th century, while over 20 concurrent civil wars were occurring at the end of the Cold War, before a significant decrease as conflicts strongly associated with the superpower rivalry came to an end. Since 1945, civil wars have resulted in the deaths of over 25 million people, as well as the forced displacement of millions more. Civil wars have further resulted in economic collapse; Burma (Myanmar), Uganda and Angola are examples of nations that were considered to have promising futures before being engulfed in civil wars.

The Angolan War of Independence (1961–1975) began as an uprising against forced cotton cultivation, and became a multi-faction struggle for control of Portugal's Overseas Province of Angola among three nationalist movements and a separatist movement. The war ended in 1975 when the Portuguese government, the National Union for the Total Independence of Angola (UNITA), the Popular Movement for the Liberation of Angola (MPLA), and the National Liberation Front of Angola (FNLA) signed the Alvor Agreement, after a leftist military coup in Lisbon in April 1974 which overthrew Portugal's Estado Novo regime.

It was a guerrilla war in which the Portuguese Armed Forces waged a counter-insurgency campaign against armed groups mostly dispersed across sparsely populated areas of the vast Angolan countryside. Many atrocities were committed by all forces involved in the conflict.

In 1482, Kingdom of Portugal's caravels commanded by Portuguese navigator Diogo Cão arrived in the Kingdom of Congo. Other expeditions followed, and close relations were soon established between the two kingdoms. The Portuguese brought firearms, many other technological advances, and a new religion, Christianity. In return, the King of the Congo offered slaves, ivory and minerals.