Born in Brest, Finistère,[1] Cornut-Gentille studied at the École Libre des Sciences Politiques.
In 1943 he was appointed as the Subprefect of Reims, but resigned to assist the Free French delegate Émile Bollaert.
[8][9] After this, he served as France's permanent representative to the United Nations Security Council,[2] and in 1957 as ambassador to Argentina.
Under Michel Debré he served as Minister of Posts, Telegraphs, and Telephones from 8 January 1959 to 5 February 1960.
He resigned ministerial office at the same time as Jacques Soustelle, over the handling of the affair of the barricades in Algiers and broke with the Gaullists.