Abstract: A motor-vehicle door comprises a structure including an inner panel (3), a carrier (5) fixed to the inner panel (3), for supporting a plurality of auxiliary members of the door, and a trimming panel (6, 7) which covers the carrier (5) and the inner panel (3) on the inner side of the door. The carrier (5) is made of fibre-reinforced synthetic material and it is rigidly connected to the inner panel (3) and it is configured to also serve as a structural reinforcement for said inner panel. The carrier (5) also has at least one portion (50, 52) exposed to view, not covered by said trimming panel (6, 7) and having a structure and a configuration such to directly serve the function of trimming panel at the exposed portions thereof. In a variant, the inner panel is constituted by a quadrangular framework constituted by one or more C-section elements defining an upper crosspiece, a lower crosspiece and two uprights which connect the ends of said crosspieces to each other.