French general, diplomat, and ultimately foreign minister under Napoleon (Napoleon I). As the Emperor's loyal master of horse from 1804, Caulaincourt was at Napoleon's side in his great battles, and his Mémoires provide an important source for the period 1812 to 1814.

In 1795 he became a cavalry conscript in western France and in 1799 was named a colonel of a crack cavalry regiment, which he led at the Battle of Hohenlinden (1800). Talleyrand, his father's friend, employed him in Russia (1801–02), where he impressed Alexander I. Napoleon took him as aide-de-camp on his return. In March 1804 he was sent to Baden to deal with royalist agents from beyond the Rhine; this led to the arrest and eventual execution of the Duc d'Enghien, an action that Caulaincourt did not wholly condone, though the orders were relayed through him.

From November 1807 to February 1811, Caulaincourt was ambassador to Russia, working incessantly for peace against Napoleon's arbitrary policy. Napoleon created him duc de Vicence (Vicenza) in 1808. Recalled in 1811, Caulaincourt was subjected to Napoleon's angry taunts that he was “Russian.” After the invasion of Russia began (1812), Caulaincourt asked to be sent to Spain, as far away from the Emperor as possible. Yet he was part of the small entourage accompanying Napoleon on his return from Russia to Paris.

Caulaincourt negotiated the armistice in Silesia (June 1813) and went to the abortive congress at Prague. After the Battle of Leipzig, he became foreign minister as the “man of peace,” but Napoleon was not peaceful, and by mid-March 1814 the congress of Châtillon had failed. Caulaincourt finally reached Alexander I and, on April 10, 1814, signed the treaty that sent Napoleon to Elba; he was with him in the last grim week at Fontainebleau. In 1815 he resumed the hopeless task of being Napoleon's foreign minister. After Waterloo Alexander's intervention saved him from the Bourbon proscription. Henceforth he lived in retirement, still trying to clear his name of complicity in the Enghien case.