The invention relates to a modular femur-head prosthesis comprising a shaft part (1) for inserting into a medullary opening of a femur and a neck part (2) comprising a receiving surface (25), said neck part being fixed to a supporting surface (15) in the end region of the shaft part (1) by means of a screw element (3). According to the invention, at least one separate intermediate ring (4) is provided, said ring being situated between the supporting surface (15) of the shaft part (1) and the receiving surface (25) of the neck part (2) and being fixed by means of the screw element (3). This allows femur head-prostheses of differing sizes to be made available by a simple substitution of a component and allows the operating surgeon to also adapt the length of the prosthesis to solve problems that are discovered intraoperatively.
