Prosthesis for the partial replacement of a vertebral body, with an upper contact plate (5) for connection to an upper vertebral body (1), a lower contact plate (6) for connection to a lower vertebral body (2), and a bridging part (7) which connects the upper and lower contact plates (5, 6) to one another and bridges at least one vertebral body (3) which is located between the upper and lower vertebral bodies (1, 2) and is to be partially replaced. The bridging part (7) is accommodated in a recess in the vertebral body (3). To be secured in said recess, it has lateral anchoring projections (9) which penetrate into the bone substance located on both sides of the bridging part (7). Its cross section narrows toward the rear preferably in a trapezoid shape.