Robert Denard (born; 7 April 1929 – 13 October 2007) was a French mercenary. He served as the de facto military leader of the Comoros twice with him first serving from 13 May 1978 to 15 December 1989 and again briefly from the 28 September to 5 October in 1995. Sometimes known under the aliases Gilbert Bourgeaud and Saïd Mustapha Mhadjou, he was known for having performed various jobs in support of Françafrique—France's sphere of influence in its former colonies in Africa—for Jacques Foccart, co-ordinator of President Charles de Gaulle's African policy.

Having served with the French Navy in the Algerian War, the ardently anti-communist Denard took part in the Katanga secession effort in the 1960s and subsequently operated in many African countries including Congo, Angola, Rhodesia (today Zimbabwe), and Gabon. Between 1975 and 1995, he participated in four coup attempts in the Comoro Islands. It is widely believed that his adventures had the implicit support of the French state, even after the 1981 election of the French Socialist Party candidate, François Mitterrand, despite moderate changes in France's policy in Africa.

Born a Roman Catholic, Denard converted first to Judaism, then to Islam, and finally back to Catholicism again. He was polygamously married seven times, and fathered eight children. Denard had a swashbuckling, larger-than-life image as the South African journalist Al J Venter called him "a warrior king out of Homer" who achieved the dream of every mercenary by conquering the Comoros in 1978, which he ruled via a puppet president until 1989. Venter believed Denard to be the most successful of the mercenaries in Africa, and certainly one of the best known.

After having served with the French Navy as a Quartermaster in the Fusiliers marins during the First Indochina War and in French Algeria, Denard served as a colonial policeman in Morocco from 1952 to 1957. He worked as a demonstrator for washing machines in Paris. In 1954, he was convicted of an assassination plot against Prime Minister Pierre Mendès-France, a left-wing member of the Radical-Socialist Party who was negotiating the end of the Indochina War and withdrawal from Morocco, Tunisia and Algeria, and served 14 months in prison. An adamant anti-communist, Denard then took part in many anti-colonialist conflicts, simultaneously on his own behalf and on that of the French state. Once he was freed from jail, he worked for the French secret services during the war in Algeria.

He began his mercenary career, which was to span three decades, in Katanga, probably in December 1961 when he and other foreign mercenaries were brought in by the leader of the mercenaries in Katanga, Roger Faulques. Denard fought there until the secessionist movement led by Moise Tshombe collapsed in January 1963. Then, Denard and his men moved to Portuguese Angola.

In mid-1963 he was in North Yemen, which was then in the middle of a civil war between a Nasserist government and royalist tribesmen. The royalists were supported by the Western European and Saudi Arabia governments. The French and British sponsored a number of mercenaries to train the royalist volunteers in military techniques, and Denard was among those who joined Imam al-Badr, leader of the royalists.

After about eighteen months Denard returned to the Congo to take employment under Tshombe who was now the prime minister of the central government in Leopoldville from July 1964 till October 1965 when he was dismissed by President Joseph Kasa-Vubu. Denard served for two years in the Congo battling Simba rebels supporters of the late Congolese leader Patrice Lumumba, who had been murdered in Katanga in 1961 after having been overthrown by rival politicians and severely tortured while in transit. The Simba rebels were backed by the Chinese and Cubans, including Che Guevara while the central government were tacitly backed by the United States and Belgium. Denard was in charge of his own unit of French mercenaries called les affreux (the awful ones). He became famous after rescuing white civilians encircled by rebels in Stanleyville (modern Kisangani) in 1963. From June 1965 he had the Polish mercenary commander Rafał Gan-Ganowicz under his orders on a one-year contract during the quelling of the Simba rebellion. Denard then supported an attempted secessionist revolt on behalf of Tshombe by Katangan separatists in July 1966.

A year later Denard sided with Katangan separatists and Belgian mercenaries led by Jean Schramme and Jerry Puren in a revolt in eastern Congo to restore Moise Tshombe to power known as the Mercenaries Revolt. The rebels were soon bottled up in Bukavu. Denard was wounded in the initial rising and flew out with a group of more seriously wounded men to Rhodesia. In January 1968 he invaded Katanga with a force of a hundred men on bicycles in an attempt to create a diversion for a breakout from Bukavu.