IOP is a three-letter acronym or initialism which may refer to:
- Inanimate Objects Party, an absurdist political party at the Rensselaer Polytechnic Institute
- Institute Of Optronics, a technical organization under Ministry of Defence Production, Government of Pakistan
- Institute of Paralegals, the oldest incorporated professional body for paralegals in the UK.
- Institute of Physics, a British professional association for physicists
- Institute of Physics, Bhubaneswar, India, a research institute in India.
- Institute of Psychiatry, part of Kings College London
- Intraocular pressure, a measure of fluid pressure in the eye
- Inherent Optical Properties
- Independent Olympic Participant, the label given to athletes who competed under the Olympic Flag in the 1992 Summer Olympics
- Invasion of privacy
- Institute of Politics
- Intensive Outpatient Program, a rehabilitation therapy most commonly used to treat chemical dependency
- Institute of Packaging a British institute for the packaging profession
- Institute of Overseas Pakistanis
- Isle of Palms, South Carolina, an island off the coast of South Carolina
In computer technology:
- Integrated Optics Package – see integrated optical circuit
- I/O processor
- Input Output Process – see SCSI
- Individual Operations – see Instruction (computer science)
- Interoperability