| O&I | Operations and Intelligence 
| Others |
| O+I | Outings and Innings
| Others |
| OI | Object Inheritance
| Others |
| OI | Object Integration
| Others |
| OI | Object Interface
| Others |
| OI | Oblique Incidence
| Others |
| OI | Obsessive Influence
| Others |
| OI | October Introduction
| Others |
| OI | Office International
| Others |
| OI | Office of Intelligence (USCS)
| Others |
| OI | Office of Investigation
| Others |
| OI | Ofsted Inspector
| Others |
| OI | Old Inteligence
| Others |
| OI | Oleum Infirmorum
| Others |
| OI | Omega Intertainment
| Others |
| OI | Online Inclusion
| Others |
| OI | Online Injection
| Others |
| OI | Online Innovation
| Others |
| OI | Open Integration
| Others |
| OI | Open Interest
| Others |
| OI | Open Interface
| Others |
| OI | Operating Income
| Others |
| OI | Operating Instruction
| Others |
| OI | Operation Insanity
| Others |
| OI | Operational Instrumentation
| Others |
| OI | Operations Information
| Others |
| OI | Operations Innovations
| Others |
| OI | Operations Interface
| Others |
| OI | Opportunistic Infection
| Others |
| OI | Opportunistic Infections
| Others |
| OI | Optical Isolator
| Others |
| OI | Optimum Interpolation
| Others |
| OI | Option Investment
| Others |
| OI | Opto Isolator
| Others |
| OI | Or Immediate
| Others |
| OI | Or Invert
| Others |
| OI | Orbiter Insertion
| Others |
| OI | Orbiter Instrumentation
| Others |
| OI | Order Information
| Others |
| OI | Ordering Information
| Others |
| OI | Orders In
| Others |
| OI | Ordinal Indicator
| Others |
| OI | Organic Initiative
| Others |
| OI | Organic Intelligence
| Others |
| OI | Oriental Institute
| Others |
| OI | Origin Independent
| Others |
| OI | Original Images
| Others |
| OI | Orthopedic Impairment
| Others |
| OI | Orthopedically Impaired
| Others |
| OI | Orthostatic Intolerance
| Others |
| OI | Osteogenesis Imperfecta
| Others |
| OI | Other Identification
| Others |
| OI | Out Of Iraq
| Others |
| OI | Out Of Iraque
| Others |
| OI | Output Input
| Others |
| OI | Outram Institute
| Others |
| OI | Outreach International
| Others |
| OI | outside in It
| Others |
| OI | Outside Influence
| Others |
| OI | Owens Illinois
| Others |