Abstract: A precast concrete gravity-base foundation is provided that is both floatable and submersible in water, and is suitable for mounting the shaft of an offshore wind turbine. The foundation comprises a bottom slab, four cylinders positioned at each corner, a centrally located cylinder, and a top slab covering each of the corner cylinders and having a central opening that receives the top portion of the centrally located cylinder. The foundation's configuration and positioning of the corner cylinders provide maximum stability, and once the corner cylinders are filled with sand, stone, or the like, the corner cylinders further bolster the overall mass and stability of the foundation. The foundation is produced on land, rolled onto a submersible jack-up barge, and transported to either a predetermined storage location or an installation site.