Expansion anchor

An expansion anchor (1) comprising a tubular body (3), which extends along a longitudinal axis (A) and displays a deformable end portion (6) on which there are obtained longitudinal slots (7) which divide the end portion (6) itself into a series of anchoring fins (8), and an expansion nut (9), which is partially engaged onto said end portion (6) and is adapted to be displaced by a screw (2) so as to radially expand said anchoring fins (8) outwards; each anchoring fin (8) being shaped so as to display an annular ridge (10) on its end and two protruding side teeth (11), which are arranged on the side edge of said anchoring fin (8) at the two ends of the ridge (10); each anchoring fin (8) further displaying an external friction surface (8a) provided with a plurality of annular notches or cavities (18) coaxial to the longitudinal axis (A).