Mazamet is a commune in the Tarn department in southern France. It is the second-largest component of the Castres-Mazamet metropolitan …Mazamet is a commune in the Tarn department in southern France. It is the second-largest component of the Castres-Mazamet metropolitan area. Mazamet is situated on the northern slope of the Montagne Noire and on the Arnette, a small tributary of the Thoré, which forms the commune's northern border.