A foundation for a windmill includes an annular pedestal, which is divided into several ring sections and is composed of prefabricated concrete elements, the pedestal including a platform for a windmill tower and several support elements extending radially outward from the pedestal, wherein the pedestal is supported by strut ribs on the support elements, wherein the pedestal, at its end forming the platform, includes a circumferential projection extending radially outward from the pedestal and including at least one channel for receiving a tensioning cable, the channel being provided in the projection and extending in the circumferential direction.