IOP
- Cromemco IOP
- IOP Publishing
- IOPS
- Industry on Parade
- Institute of Optronics
- Institute of Physics
- Institute of Physics (disambiguation)
- Institute of Physics, Bhubaneswar
- Institute of Play
- Institute of Politics (disambiguation)
- Institute of Psychiatry, Psychology and Neuroscience
- Intensive outpatient program
- Intraocular pressure
- Isle of Palms, South Carolina
- Italian occult psychedelia
- List of IOC country codes
- Portfolio (finance)
- UGV Interoperability Profile