Born on 27 May 1760 in Rouen into an upper-middle-class family, Cauchy successfully studied at the Collège de Lisieux in Paris. In 1771 he received the top prize in the concours général.
He became a lawyer at the Parlement of Normandy, and in 1783 he joined the office of the Intendant Général of Rouen, Louis Thiroux de Crosne. When de Crosne took charge of the Parispolice, Cauchy followed him as his senior aide. In October 1787 he married Marie-Madeleine Desestre, who came from a family of Parisian officers, and the couple had four children, Augustin-Louis Cauchy (1789-1857), Alexandre Laurent Cauchy (1792-1857), Eugène François Cauchy (1802-1877) and a daughter.