He had been suffering from Alzheimer’s disease.
Mr Denard, whose real name was Gilbert Bourgeaud, became famous as a soldier for hire in a succession of post-colonial war theatres, including Congo, Angola and Nigeria, as well as in Iran and Yemen.
He also took part in four coups or coup attempts in the Comoros Islands, where he served for a time as head of the presidential guard.
In 2006, he was given a suspended five-year jail term in Paris for a failed 1995 putsch in the Comoros. This was increased at an appeal court last July to a year in jail with three suspended, but he never served it due to ill health.
Born in the south-western city of Bordeaux in 1929, Mr Denard joined the Free French Forces in Indochina at the end of World War II and served in the army until 1952.
A fervent anti-communist, he began his mercenary career in 1960 helping secessionists in the Katanga region of Congo, and in 1964 was backing royalists in Yemen.
Over the next decades he is believed to have seen action in the former Rhodesia (Zimbabwe), Nigeria, Benin, Angola, Zaire and the Comoros. He is regarded as the model for the hero of British author Frederick Forsyth’s book The Dogs of War.
Though nothing wasadmitted, it is believed that many of his adventures had the tacit approval of theauthorities in Paris andespecially of Jacques Foccart — president Charles de Gaulle’s Africa pointman — who was anxious to maintain French influence on the continent.
During his three-week trial in February last year, the defence produced a former head of foreign intelligence who said: “When special services are unable to undertake certain kinds of undercover operation, they use parallel structures. This was the case of Bob Denard.”
In his autobiography,Mr Denard himself said that: “Often I didn’t exactly have a green light fromthe French authorities,but I went on the amber.”
After the 1981 election of Socialist president Francois Mitterrand, Mr Denard’s privileged contacts in Paris declined, but for many years he remained an influential figure in the Comoros.
He first staged a coup there in 1975 — just after the country’s declaration of independence from France and probably at French instigation — and again in 1978 to restore the ousted first president Ahmed Abdallah. He then became head of Mr Abdallah’s presidential guard, converting to Islam, taking the name Said Mustapha Mahdjoub and forging a strategic alliance with South Africa. But in 1989 Mr Abdallah was assassinated in murky circumstances and Mr Denard fled.
In 1995 he came out of retirement at the age of 66 for a last throw of the dice in the Comoros, landing on a beach with 30 soldiers in rubber dinghies. This final putsch failed when the French army intervened after a week.
Married seven times and the father of eight children, Mr Denard divided his last years between Paris and his home in the Medoc wine-growing region of south-west France.