A radiation diaphragm for an X-ray apparatus has an absorber element that can be swiveled around a swiveling axis for the variable limitation of a ray bundle. The swiveling axis is oriented transversely to the ray bundle. A swivel arm that can be swiveled around the swiveling axis and that carries the absorber element. The absorber element can comprise a curved shape. Such a radiation diaphragm allows an especially effective radiation dose limitation for the patient.