Born in Saint-Sauveur-Lendelin, after studies of philosophy at the Collège de Navarre, he started his career during the Ancien Régime, making his first appearance as a lawyer in Paris in 1762. He filled the posts of censeur du Roi and then Inspector General of the Domains of the Crown. During the early 1760s, Lebrun became a disciple of Montesquieu and an admirer of the British Constitution, travelling through Southern Netherlands, the Dutch Republic, and finally to the Kingdom of Great Britain. He became one of Chancellor René Nicolas de Maupéou's chief advisers, taking part in his struggle against the parlements and sharing his downfall in 1774. Lebrun then devoted himself to literature, translating Torquato Tasso's Jerusalem Delivered and the Iliad. He retreated from public life to his property in Grillon, attempting to live a life as envisaged by the philosophe Jean-Jacques Rousseau. During the cabinet of Jacques Necker, he was consulted on several occasions, but never appointed to high office.
A suspect during the Reign of Terror, he was twice arrested: the first time in September 1793, liberated after the intervention of Joseph Augustin Crassous ; the second time in June 1794 - threatened with the guillotine, he was saved by a relative of his who stole his record of prosecution, thus causing a delay long enough for Lebrun to be saved by the Thermidorian Reaction. In 1795, Lebrun was elected as a deputy to the French Directory's Council of Ancients and, although a supporter of the House of Bourbon, he voted against prosecutions of Jacobins, and showed himself in favour of national reconciliation.
Consulate, Empire, and Restoration
Lebrun was made Third Consul following Napoleon Bonaparte's 18 Brumaire coup in the Year VIII. In this capacity, he took an active part in Napoleon's reorganization of the national finances and in the administration of France's départements. He was made a member of the Académie des Inscriptions et Belles-Lettres in 1803, and in 1804, he was appointed Arch-Treasurer of the French Empire. From 1805 to 1806, he was governor-general of Liguria, during which time he completed its annexation by France. He opposed Napoleon's restoration of the noblesse and, in 1808, only reluctantly accepted the title of duc de Plaisance, a rare, nominal, but hereditary duché grand-fief, extinguished in 1926. From 1811 to 1813, he served as governor-general of a part of the annexed Netherlands, reorganizing its départements - Zuyderzée and Bouches-de-la-Meuse. He was assisted by Antoine de Celles and Goswin de Stassart. Although to a certain extent opposed to the autocracy of the Emperor, he was not in favor of his deposition, although he accepted the fait accompli of the Bourbon Restoration in April 1814. Louis XVIII made him a Peer of France, but during the subsequent Hundred Days, he accepted from Napoleon the post of grand maître de l'Université. As a consequence, he was suspended from the House of Peers when the Bourbons returned again in 1815, but was recalled in 1819. He died five years later in Sainte-Mesme.