The son of a Swiss officer in the Dutch service, whose family was of French origin, he studied at Erlangen, Ger., briefly at the University of Oxford, and at Edinburgh. In 1787 he formed, in Paris, his first liaison, with Madame de Charrière, 27 years his senior. His republican opinions in no way suited him to the office of chamberlain to the duke of Brunswick, which he held for several years. In 1794 he chose the side of the French Revolution, abandoning his office and divorcing his wife, a lady of the court. Madame de Staël (Staël, Germaine de) had much to do with his decision. Their tumultuous and passionate relationship lasted until 1806.

After the coup d'état of 18 Brumaire (1799), Constant was nominated to the tribunate, but he quickly became, like Madame de Staël, an opponent of the Bonapartist regime. Expelled from the tribunate in 1802, he followed her into exile the year after. Thereafter he spent his time either at Madame de Staël's salon at Coppet, near Geneva, or in Germany, chiefly at Weimar, where he met Goethe and Friedrich Schiller. Constant was the associate of the brothers Friedrich and August von Schlegel, the pioneers of the Romantic idea, and with them he inspired Madame de Staël's book De l'Allemagne (“On Germany”).

In 1808 Constant secretly married Charlotte von Hardenberg. But his intellectual relationship with Madame de Staël and the group at Coppet remained unbroken. As a liberal he was disappointed by the restoration of the Bourbon monarchy in 1814, and he reconciled himself with the Napoleonic empire of the Hundred Days under the influence of Madame Récamier, the other great love of his life. On his return to Paris, Constant became one of the leaders of liberal journalism. He was elected a deputy in 1819. After the revolution of July 1830, he was appointed president of the council of state but died the same year.

During his exile, Constant began work on De la religion considérée dans sa source, ses formes, et ses développements, 5 vol. (1824–31; “On Religion Considered in Its Source, Its Forms, and Its Developments”), a historical analysis of religious feeling. He is better known, however, for his novels. Published in 1816 and written in a lucid and classical style, the autobiographical Adolphe (Eng. trans. Adolphe) describes in minute analytical detail a young man's passion for a woman older than himself. Nearly 150 years after the publication of Adolphe, another of Constant's autobiographical novels, Cécile, dealing with events between 1793 and 1808, was discovered and first published. Constant is also known for his Journaux intimes (“Intimate Journals”), first published in their entirety in 1952. They add to the autobiographical picture of Constant provided by his Le Cahier rouge (1907; The Red Notebook).