The invention relates to a vehicle occupant protection system, comprising a gas bag which has at least one inflatable chamber defined by a wall. The protection system further comprises a tensioning strap which fixes the gas bag in position in an inflated state. The tensioning strap is fully looped around the wall of the chamber and fastened to the wall and to the vehicle in such a manner that inflating the chamber causes a displacement of the tensioning strap and a tightening of the tensioning strap.