An orthotopic artificial bladder endoprosthesis includes a base obtained with a multi-layered silicone membrane having an external surface and an internal surface both coated with pyrolytic turbostratic carbon; a resorbable cap obtained with a PGA fiber fabric, the base and the cap being connected with each other along respective edges, to define a closed enclosure; the base is connectable to the urethra and to the ureters of a patient; the base also being of substantially triangular form.