La Guerche-de-Bretagne is a commune in the Ille-et-Vilaine department in Brittany in northwestern France. The cellist Louis-Marie Pilet was bor…La Guerche-de-Bretagne is a commune in the Ille-et-Vilaine department in Brittany in northwestern France. The cellist Louis-Marie Pilet was born in La Guerche-de-Bretagne. Inhabitants of La Guerche-de-Bretagne are called Guerchais in French.