A motor vehicle chassis includes two side rail members covered at the front by two lateral floor reinforcements, a rear central cross member and a transverse reinforcement which is welded to the two lateral floor reinforcements, and a floor having a seat-cushion support part. The chassis further includes a rear raiser welded to the rear central cross member and two lateral raisers welded respectively to each of the two lateral floor reinforcements. The seat-cushion support part of the floor is welded to the two lateral raisers, to the rear raiser and to the transverse reinforcement, so as to create a space for an energy reservoir under the seat-cushion support part of the floor.