Adrien Duport (born Feb. 5, 1759, Paris—died Aug. 15, 1798, Appenzell, Switz.) was a French magistrate who was a leading constitutional monarchist during the early stages of the French Revolution of 1789.

A prominent member of the Parlement of Paris (one of the high courts of justice), Duport was elected for the nobility to the Estates-General of 1789. On June 25 he and 46 other representatives of the nobility joined the unprivileged Third Estate, which had already declared itself a revolutionary National Assembly. As one of the Assembly’s most brilliant lawyers, Duport played a major role in creating the judicial machinery that supplanted the legal system of the ancien régime.

Nevertheless, by the spring of 1791, Duport and his two close associates, Antoine Barnave and Alexandre, comte de Lameth—the “triumvirate”—felt that further democratic reforms would endanger the monarchy and private property. They became secret advisers to King Louis XVI and formed the Club of the Feuillants with their royalist allies. Duport became president of the criminal court of Paris, but he fled to England—probably with the help of the democratic leader Georges Danton—soon after the fall of the monarchy on Aug. 10, 1792. He returned to France after the radical democrat Robespierre fell from power on 9 Thermidor (July 27, 1794). On the military coup d’état of 18 Fructidor, year V (Sept. 4, 1797), he fled to Switzerland.