An implantable prosthesis for use in positioning a breast implant comprising a sheet of a prosthetic material configured to form a sling-shaped receiving area for receiving and supporting the breast implant. The surface area of the implantable prosthesis contacting the breast implant comprises a biocompatible or chemically inert material to prevent abrasion of or reaction with the breast implant. The implantable prosthesis of the present invention can be used during corrective procedures to reposition and support a malpositioned breast implant or during reconstructive or cosmetic procedures at the time the implant is first positioned within the patient. The prosthesis is used with implants in the partial sub-muscular, completely sub-muscular, and sub-glandular position and is used to prevent medial, lateral and inferior displacement of the implant.