Altering patient's facial profile has been a challenge for orthodontists over the years. Each clinician is periodically confronted with malocclusions that do not respond favorably to only tooth moving mechanotherapies because of the disharmony actually existing in the basal jaw bone itself. The aim is to correctly position the jaws anterio-posteriorly and vertically with correct overbite, overjet and centric relation. A major reason for development of functional appliances was recognition that function had an effect on ultimate morphologic structure of dentofacial complex. Functional appliances refer to a variety of appliances designed to alter the arrangement of various muscle groups that influence the function and position of the mandible in order to transmit forces to dentition and basal bone. This book reviews various fixed functional appliances used in the field of orthodontics.