An ankle-foot orthosis (AFO) is an externally applied orthopedic appliance which is designed to protect, support and prevent or correct deformity of the foot, ankle and lower leg complex. AFOs are commonly refered to as braces or splints and can be made from either plastics or metal and leather. Various hinge designs are also available for AFOs which allow articulation at the ankle joint. New advances in design are an ongoing process.

AFOs are commonly used to provide support for footdrop or for ankle instability associated with several conditions some of which include stroke, spina bifida, cerebral palsy, Lou Gehrig's Disease(ALS), multiple sclerosis, paraplegia or polio.