Mr Giscard d’Estaing had recently been taken to hospital in Tours, in central France. His office did not provide any further details.
Born in 1926, Mr Giscard d’Estaing served in the Free French army that helped liberate France during the Second World War.
Charles de Gaulle named him finance minister at age 36.
As president, he helped forge a single Europe with his close friend, German Chancellor Helmut Schmidt.