Abstract: The present invention relates to a self-locking coupling structure for connecting accessories to profiled elements which has the peculiarity of comprising a body which defines a protrusion which can be inserted between the opposite wings which delimit a seat on a profiled element. The protrusion has a curved surface which is delimited, on one side, by an engagement portion which can be inserted below one of the wings by rotation about an axis which is substantially parallel to the longitudinal extension of the profiled element and is suitable for generating a localized deformation of the wing substantially in the portion affected by the longitudinal extension of the protrusion, and, on the other side, by a stop portion which can engage below the other wing. The protrusion, in locking position, abuts against the bottom of the seat in at least two points which are mutually spaced in a transverse direction with respect to the longitudinal extension of the profiled element.