An airbag for a vehicle occupant restraint system of a motor vehicle is provided. The airbag comprising at least one first and one second layer of an airbag material, at least one inflatable chamber formed between the first and the second layer, which is inflatable for the protection of a vehicle occupant and at least one seam, by which the first and the second layer are connected with each other along at least a portion of their respective circumference. The airbag is deployed between a vehicle occupant and a vehicle side structure. The airbag is formed such that when the airbag is mounted in the vehicle and inflated, the seam extends along a plane which is oriented obliquely or transversely to a plane formed by the longitudinal and the height direction of the vehicle.