Zaire, officially the Republic of Zaire, formerly Republic of the Congo (Léopoldville) and now called the Democratic Republic of the Congo, was a state in central Africa from 1971 to 1997. It was, by area, the third-largest country in Africa after Sudan and Algeria, and the 11th-largest country in the world from 1965 to 1991. With a population of over 23 million, Zaire was the most populous Francophone country in Africa. Zaire was strategically important to the West during the Cold War, particularly the U.S., as a counterbalance to Soviet influence in Africa. The U.S. and its allies supported the Mobutu Regime (1965–1997) with military and economic aid to prevent the spread of communism.

The country was a one-party totalitarian military dictatorship, run by Mobutu Sese Seko and his Popular Movement of the Revolution. Zaire was established following Mobutu's seizure of power in a military coup in 1965, after five years of political upheaval following independence from Belgium known as the Congo Crisis. Zaire had a strongly centralist constitution, and foreign assets were nationalized. The period is sometimes referred to as the Second Congolese Republic.

A wider campaign of Authenticité, ridding the country of the influences from the colonial era of the Belgian Congo, was also launched under Mobutu's direction. Weakened by the termination of American support after the end of the Cold War, Mobutu was forced to declare a new republic in 1990 to cope with demands for change. By the time of its downfall, Zaire was characterised by widespread cronyism, corruption and economic mismanagement.

Zaire collapsed in the 1990s, amid the destabilization of the eastern parts of the country in the aftermath of the Rwandan genocide and growing ethnic violence. In 1996, Laurent-Désiré Kabila, the head of the AFDL militia, led a popular rebellion against Mobutu. With rebel forces making gains westward, Mobutu fled the country, leaving Kabila's forces in charge. In 1997, the country's name was restored to the Democratic Republic of the Congo; Mobutu died less than four months later while in exile in Morocco.

The country's name, Zaïre, was derived from the name of the Congo River, sometimes called Zaire in Portuguese, which in turn was derived from the Kikongo nzere o zadi ('river that swallows rivers'). The use of Congo seems to have replaced Zaire gradually in English usage during the 18th century and Congo was the preferred English name in 19th-century literature, although references to Zahir or Zaire as the name used by the local population (i.e. derived from Portuguese usage) remained common.

In 1965, as in 1960, the division of power in Congo-Léopoldville (a former Belgian colony) between President and Parliament led to a stalemate and threatened the country's stability. Joseph-Désiré Mobutu again seized power. Unlike the first time, however, Mobutu assumed the presidency, rather than remaining behind the scenes. From 1965, Mobutu dominated the political life of the country, restructuring the state on more than one occasion, and claiming the title of "Father of the Nation". He announced the renaming of the country as the Republic of Zaire on 27 October 1971.

When, under the authenticité policy of the early 1970s, Zairians were obliged to adopt "authentic" African names rather than European monikers. Mobutu dropped Joseph-Désiré and officially changed his name to Mobutu Sese Seko Kuku Ngbendu Wa Za Banga, or, more commonly, Mobutu Sésé Seko, roughly meaning "the all-conquering warrior, who goes from triumph to triumph".

In retrospective justification of his 1965 seizure of power, Mobutu later summed up the record of the First Republic as one of "chaos, disorder, negligence, and incompetence". Rejection of the legacy of the First Republic went far beyond rhetoric. In the first two years of its existence, the new regime turned to the urgent tasks of political reconstruction and consolidation. Creating a new basis of legitimacy for the state, in the form of a single party, came next in Mobutu's order of priority.