Disclosed is an external breast prosthesis (1), including an envelope (2) of flexible material with a breast shape, the envelope defining an internal cavity (6) closed by a protective lid (3) of which one face, called the external face (4), is designed to be pressed against the chest of a person, the cavity enclosing a filler and a weighted element intended to adjust the weight of the prosthesis. The weighted element is in the form of a plurality of ballast elements (7) which are distributed along a sagittal axis of the prosthesis substantially perpendicular to the plane of the protective lid.