Orthodontics, orthodontia, or orthodonture (from Greek orthos "straight or proper"; and odous "tooth") is the first specialty of dentistry that is concerned with the study and treatment of malocclusions (improper bites), which may be a result of tooth irregularity, disproportionate jaw relationships, or both. Orthodontic treatment can focus on dental displacement only, or can deal with the control and modification of facial growth.

In the latter case it is better defined as "dentofacial orthopaedics". Orthodontic treatment can be carried out for purely aesthetic reasons with regards to improving the general appearance of patients' teeth. However, there are orthodontists who work on reconstructing the entire face rather than focusing exclusively on teeth.