| OPA | Oak Pears Apple 
| Others |
| OPA | Oatmeal Pale Ale
| Others |
| OPA | Odyssey Public Access
| Others |
| OPA | Office of Payroll Administration
| Others |
| OPA | Office of Penalty Administration
| Others |
| OPA | Office of Personal Adherence
| Others |
| OPA | Office of Pharmacy Affairs
| Others |
| OPA | Office of Police Accountability
| Others |
| OPA | Office of Population Affairs
| Others |
| OPA | Office of Population Affairs (Department of Health and Human Services)
| Others |
| OPA | Office of Postdoctoral Affairs
| Others |
| OPA | Office of Prestigious Awards
| Others |
| OPA | Office of Price Administration
| Others |
| OPA | Office of Price Authority
| Others |
| OPA | Office of Professional Accountability
| Others |
| OPA | Office of Property Assessment
| Others |
| OPA | Office of Public Affairs
| Others |
| OPA | Office of the Patient Advocate
| Others |
| OPA | Office product activation
| Others |
| OPA | Official Plan Amendment
| Others |
| OPA | Official Police Action
| Others |
| OPA | Ogrydziak Prillinger Architects
| Others |
| OPA | Ohio Pawnbrokers Association
| Others |
| OPA | Ohio Pharmacists Association
| Others |
| OPA | Ohio Psychological Association
| Others |
| OPA | Oil Painters of America
| Others |
| OPA | Oil Pollution Act
| Others |
| OPA | Oil Pollution Act of 1990
| Others |
| OPA | Oil Producers Association
| Others |
| OPA | Oklahoma Psychological Association
| Others |
| OPA | Oligo Pool All
| Others |
| OPA | Oliva Perez and Agansora
| Others |
| OPA | Omni Path Architecture
| Others |
| OPA | On Page Ace
| Others |
| OPA | One Pot Application
| Others |
| OPA | Online Pak Ads
| Others |
| OPA | Online Payment Agreement
| Others |
| OPA | Online Personal Access
| Others |
| OPA | Online Poker Analyzer
| Others |
| OPA | Online Pool Analyzer
| Others |
| OPA | Online Presence Audit
| Others |
| OPA | Online Privacy Alliance
| Others |
| OPA | Online Public Access
| Others |
| OPA | Online Publishers Association
| Others |
| OPA | Ontario Power Authority
| Others |
| OPA | Open Platform for Architecture
| Others |
| OPA | Open Policy Agent
| Others |
| OPA | Operations Planning Analysis
| Others |
| OPA | Optical Phased Array
| Others |
| OPA | Optical Power Adjustment
| Others |
| OPA | Optical Pre Amplifier
| Others |
| OPA | Optimal Performance Architecture
| Others |
| OPA | Optionally Piloted Aircraft
| Others |
| OPA | Oracle Policy Automation
| Others |
| OPA | Oracle Protocol Adapter
| Others |
| OPA | Oral Proficiency Assessment
| Others |
| OPA | Oregon Paralegal Association
| Others |
| OPA | Oregon Pilots Association
| Others |
| OPA | Oregon Psychological Association
| Others |
| OPA | Organization for Professional Astrology
| Others |
| OPA | Organizational Process Assets
| Document, Management, Process, Project |
| OPA | Orientation Peer Advisor
| Others |
| OPA | Oro Pharyngeal Airway
| Others |
| OPA | OroPharyngeal Airway
| Others |
| OPA | Orthopedic Physicians Alaska
| Others |
| OPA | Other Peoples' Attraction
| Others |
| OPA | Other Principal Arterial
| Others |
| OPA | Other Principle Arterial
| Others |
| OPA | Other Procurement Authority
| Others |
| OPA | Other Procurement, Army
| Others |
| OPA | Outcome Purpose Action
| Others |
| OPA | Outcome Purpose and Action
| Others |
| OPA | Outcome, Purpose, Action
| Others |
| OPA | Outcome, Purpose, and Action
| Others |
| OPA | Outer Planets Alliance
| Others |
| OPA | Outpatient Appointment
| Others |
| OPA | Overseas Performing Artist
| Others |
| OPA | Oxford Preparatory Academy
| Others |
| OPA | Psion OPL Object file
| Others |