Ortho (from the Greek word ὀρθός meaning "straight" or "correct") may refer to:
In computer science
- Orthodontics, a specialty of dentistry concerned with the study and treatment of malocclusions
- Orthopedic, the study of the musculoskeletal system.
- Ortho-DOT, a psychedelic drug
- Ortho-cept and Ortho Tri-cyclen, kinds of oral contraceptive drug