| Acronym | Definition |
|---|
| OI | Owens-Illinois, Inc. (glass container and plastics manufacturer) |
| OI | Oriental Institute |
| OI | Oral Irrigator (dentistry) |
| OI | Open Interest (finance) |
| OI | Osteogenesis Imperfecta (brittle bone bisease) |
| OI | Operation Ivy (Ska band) |
| OI | Openindiana (open source computing) |
| OI | Outside in (Frisbee throw) |
| OI | Office of Investigations |
| OI | Old Irish (dialect) |
| OI | Opportunistic Infection |
| OI | Oceanology International (periodic conference and trade show) |
| OI | Operating Income |
| OI | Office of Information |
| OI | Optical Illusion |
| OI | Oxfam International (UK) |
| OI | Operator Interface |
| OI | Ovulation Induction (fertility treatment) |
| OI | Optimist International (St. Louis, MO) |
| OI | Other Insurance |
| OI | Optimum Interpolation |
| OI | Ordinary Income (US IRS) |
| OI | Oxygen Index |
| OI | Opportunity International (Oak Brook, IL) |
| OI | Office of Intelligence (USCS) |
| OI | Oratorical Interpretatioin (high school forensics) |
| OI | Operating Instruction |
| OI | Off Invoice (promotion) |
| OI | Orphans International |
| OI | Operations Interface |
| OI | Orcas Island (Washington) |
| OI | Objeto Indirecto (Spanish grammar) |
| OI | Osmose Inverse (French: Reverse Osmosis) |
| OI | Optical Isolator (Telcordia) |
| OI | Ore Ida (food brand) |
| OI | Optical Interface |
| OI | Other Investigation (US IRS) |
| OI | Outside Information |
| OI | Opening Instructions |
| OI | Operations Integration |
| OI | Ockenden International (UK registered charity) |
| OI | Operational Instruction |
| OI | Opto-Isolator (electronics) |
| OI | Office Interface |
| OI | Operational Issue |
| OI | Operational Instrumentation |
| OI | Organization Identifier (ASN.1) |
| OI | Opportunity Illuminator (radar) |
| OI | Output Isolation |
| OI | Order for Information (EPA) |
| OI | Operator Interrupt (telecommunications) |
| OI | Outline of Investigation |
| OI | Organizational Integrator |
| OI | Organization Indicator |
| OI | Optical Improvements |
| OI | Optical Improved |
| OI | OFISA Informatique (Lausanne, Switzerland) |
| OI | Organizationally Impaired |
| OI | Outreach International, Inc. (Independence, MO) |
| OI | Orbit Infotech (New Delhi, India) |