Fleury-Mérogis Prison (Maison d'arrêt de Fleury-Mérogis) is a prison in France, located in the town of Fleury-Mérogis, in the southern suburbs of Paris. With more than 4,100 prisoners, it is the largest prison in France. It is operated by the Ministry of Justice. Fleury-Mérogis is notorious as a leading center of Islamist radicalization in European prisons.