Armand Augustin Lonis De Caulalycourt, duke of Vicenza, a French general and diplomatist, born at Caulaincourt, near Saint-Quentin, in 1773, died in Paris, Feb. 19, 1827. His father, the marquis of Caulaincourt, was a general officer, and the son served in the army from an early age, both in the ranks, under the conscription, and as a staff officer. He was imprisoned for a time after 1792, but followed Gen. Aubert du Bayet to Constantinople in 1797, and made the campaign of 1800 under Gen. Moreau, and those of 1805, 180G, and 1807 under Napoleon. Upon the accession of the emperor Alexander in 1801, he was sent as diplomatic agent to St. Petersburg. He was afterward appointed by Napoleon grand equerry and duke of Vicenza, and in 1807 was sent as ambassador to Russia, in the place of the duke of Rovigo. Being suspected of complicity in the death of the duke d'Enghien, he was coldly received by the Russian nobility, until Alexander wrote him a letter declaratory of his innocence, and gave him special marks of personal esteem. He subsequently disapproved of the foreign policy of Napoleon, and in 1811 asked to be recalled.

He also opposed the invasion of Russia. After the burning of Moscow Napoleon chose him as his companion on his flight to France. He was plenipotentiary to the allied sovereigns during the campaign of Saxony, signed the armistice of Plaswitz, June 4, 1813, and was appointed French plenipotentiary to the abortive congress of Prague. He was attached to the person of Napoleon in the campaign that followed. On April 5, 1813, he was made senator, and in September minister of foreign affairs, and in this capacity he went to the congress of Chatillon. When Napoleon seemed about to abdicate, Caulaincourt used his influence with the emperor Alexander to secure the best terms possible, and it is thought that the sovereignty of Elba was secured by his efforts. He signed the treaty of April 11, 1814, and retired to his country seat. On the return of Napoleon in 1815 he was again made minister of foreign affairs. His circular of April 3 to the French diplomats abroad represented the second accession of Napoleon in the best light, and gave assurance of respect for the rights of other nations.

He took part in the deliberations of the two chambers in regard to the second abdication, and was a member of the commission of government which preceded the second return of Louis XVIII. His name was upon the list of July 24, but by the influence of the emperor Alexander it was erased. From this time his life was wholly private, except that the old accusation of complicity in the death of the duke d'Enghien was revived; upon which he published the letter of Alexander exonerating him. This accusation weighed upon him, and he referred to it in his will, protesting his entire innocence. He left unpublished memoirs, said to be of value.