Jean Joseph Mounier (12 November 1758 – 28 January 1806) was a French politician and judge.
Mounier was born in Grenoble in Southeastern France. He studied law, and in 1783 obtained a judgeship at Grenoble. He took part in the struggle between the parlements and the court in 1788, and promoted the meeting of the estates of Dauphiné at Vizille (20 July 1788), on the eve of the French Revolution. He was secretary of the assembly, and drafted the cahiers ("notebooks") of grievances and remonstrances presented by it to King Louis XVI. Thus brought into prominence, Mounier was unanimously elected deputy of the third estate to the states general of 1789; Mounier also founded the Monarchiens party in August 1789.
There, and in the Constituent Assembly, he was at first an upholder of the new ideas, pronouncing himself in favour of the union of the Third Estate with the two privileged orders, proposing the famous Tennis Court Oath, assisting in the preparation of the new constitution, and demanding the return of Jacques Necker. On 28 September 1789 he was elected president of the Constituent Assembly. Being unable to approve the proceedings which followed, Mounier withdrew to Dauphiné, resigned as deputy, and, becoming suspect, took refuge in Switzerland in 1790.
He returned to France in 1801. Napoleon Bonaparte named him prefect of the department of Ille-et-Vilaine, which he reorganized, and in 1805, he was appointed councillor of state. He died in Paris. His principal writings are Considérations sur les gouvernements (1789); Recherches sur les causes qui ont empeché les Français de devenir libres (1792), and De l'influence attribuée aux philosophes, aux francs-maçons et aux illuminés sur la Révolution Française. (1801).