| Abbreviation | Definition |
|---|---|
| OPUS | Officer Program for Undergraduate Students |
| OPUS | Online Pathway for University Students |
| OPUS | Online Publications University of Stuttgart |
| OPUS | Open Portal to University Scholarship |
| OQH | Online Quiz Hell |
| OQM | Old Quantum Mechanics |
| OR | Operations Research |
| ORAU | Oak Ridge Associated Universities |
| ORC | Operations Research Center |
| ORG | Operations Research Group |
| ORGA | Office of Research and Grants Administration |
| ORI | Ocean Research Institute, University of Tokyo |
| ORI | Office of Research Integrity |
| ORIF | Oilseed Research Institute Faisalabad |
| ORION | Ontario Research and Innovation Optical Network |
| ORIS | Office of Research Information Services (UW) |
| ORL | Operations Research Laboratory |
| ORS | Office for Research Support |
| ORU | Oral Roberts University |
| ORU | Organized Research Unit |