Airbag and airbag module for a motor vehicle having such an airbag

The invention relates to an airbag (14) for unfolding between a vehicle part (10) and a vehicle occupant (18), comprising an impact wall (20) which, in the installed and unfolded state of the airbag (14), faces a vehicle occupant (18) and a circumferential wall (22) which is connected to the impact wall (20) and, in the installed and unfolded state of the airbag (14), extends between the impact wall (20) and the vehicle part (10), wherein the circumferential wall (22) is made with multiple layers, at least in some sections, and forms at least one annular tube (23) which delimits an annular inflatable first airbag volume (V1), and wherein a radially inner layer (26) of the circumferential wall (22), together with the impact wall (20), delimits an inflatable second airbag volume (V2) that is separate from the first airbag volume (V1). The invention further relates to an airbag module (12) having such an airbag (14).