Saint-Grégoire is a commune in the department of Ille-et-Vilaine, Brittany, northwestern France. Inhabitants of Saint-Grégoire are called grégori…Saint-Grégoire is a commune in the department of Ille-et-Vilaine, Brittany, northwestern France. Inhabitants of Saint-Grégoire are called grégoriens in French. The city hosts offices of important firms such as KPMG, or the "Banque Populaire Grand Ouest" and others well-known firms that make the commune important regarding the other communes around.