Abstract: Airbag with adjustable safety valve comprising a vent aperture made in the fabric of the airbag, at least one membrane of an elastic material attached to said fabric at a union area, said membrane being stretched across the width of said vent aperture and defining a variable area with an orifice that is smaller than the vent aperture, the orifice being deformed and growing with the pressure increase in the airbag, characterized in that between the variable area and the union areas, the membrane has a reinforcement area in the form of a containment ring with a greater thickness than that of the variable area, which controls the maximum aperture of the orifice.